Meiosis & Mitosis – Chromosomes in Anaphase & Metaphase – Biochemistry
These Biochemistry chapters discuss Meiosis & Mitosis – chromosomes in Anaphase, Metaphase, Prophase & Telophase, chromatids, parent & daughter cells.
All of the following may be found in a DNA nucleotide EXCEPT
D) phospholipid. – Correct
Genetic inheritance is based on what type of molecule?
A) DNA – Correct
The repeating sequence of cells dividing, growing, and dividing again is called
A) stem cell differentiation.
B) the cell cycle. – Correct
C) homologous differentiation.
Cells with two of each kind of chromosome are described by the term
D) diploid. – Correct
The terminal ends or “tips” of a chromosome are called
C) telomeres. – Correct
A portion of a DNA molecule wound around a “bead” of histone protein is called a
D) cell cycle.
E) nucleosome – Correct
Which of the following is the proper sequence for mitosis (I. metaphase, II. telophase, III. prophase, IV. anaphase)?
A) I, III, IV, II
B) III, IV, I, II
C) IV, I, III, II
D) III, I, IV, II – Correct
E) I, II, III, IV
The two main stages of the cell cycle are called
A) mitosis and interphase. – Correct
B) telophase and cytokinesis.
C) interphase and anaphase.
D) cytokinesis and mitosis.
The distribution of cytoplasm to daughter cells is accomplished during
A) mitosis. – Correct
E) prokaryotic fission.
The spindle apparatus is made of
A) microtubules. – Correct
C) Golgi bodies.
D) endoplasmic reticulum.
In mitosis, if a parent cell has 16 chromosomes, each daughter cell will have how many chromosomes?
D) 16 – Correct
Cancer is essentially
A) the binding of cyclins and Cdks.
B) a never-ending repetition of the S phase of the cell cycle.
C) unregulated mitotic cell division. – Correct
D) the creation of extra checkpoints in the cell cycle
Different, or alternative, forms of the same gene are called
C) alleles. – Correct
A) results in new combinations of genetic traits. – Correct
B) leads to uniform characteristics in a population.
C) produces genetic clones.
D) requires less tissue differentiation than asexual reproduction.
E) produces genetic clones and requires less tissue differentiation than asexual reproduction
In humans, the male determines the sex of the child because males have
A) 46 chromosomes.
B) one X and one Y chromosome. – Correct
C) two X chromosomes.
D) two Y chromosomes.
A photograph of all the stained, prepared chromosomes in a eukaryotic cell is referred to as a
D) karyotype – Correct
Chiasmata (or chiasma) provide evidence of
A) chromosomal aberration.
B) Crossing over. – Correct
D) spindle fiber formation.
When gametes fuse during fertilization, a(n)___is produced
C) Zygote – Correct
D) haploid individual
What is a major difference between mitosis and meiosis?
A) Meiosis produces two daughter cells instead of the four daughter cells produced in mitosis
B) Meiosis produces genetically identical daughter cells, whereas mitosis produces genetically variable daughter
C) Mitosis produces daughter cells, whereas meiosis produces parent cells
D) Meiosis produces haploid cells, whereas mitosis produces diploid cells – Correct
According to the law of segregation, in an organism with the genotype Aa
A) all of the gametes get the A allele.
B) all of the gametes get the a allele
C) one-half of the gametes get the A allele and one-half get the a allele – Correct
D) three-quarters of the gametes get the A allele and one-quarter get the a allele.
E) one-quarter of the gametes get the A allele and three-quarters get the a allele
A recessive allele is one
A) that is not expressed as strongly as a dominant allele.
B) whose effect is masked when paired with a dominant allele. – Correct
C) that appears only in a heterozygote.
D) that produces no effect when present in the homozygous condition.
E) that must be lethal in the homozygous condition
The physical manifestation of an organism’s genes is its
C) phenotype. – Correct
D) genetic code.
E) number of chromosomes.
The genetic makeup of an individual is the
B) sex cell.
D) gene pool.
E) genotype. – Correct
Which of the following is TRUE of genes that are physically located close to each other on the same chromosome?
A) They tend to not be inherited together.
B) They are not linked.
C) Expressed differently in males than in females.
D) They are linked and tend to be inherited together – Correct
Codominance occurs when
A) both of the alleles in a heterozygote are equally expressed phenotypically in an individual. – Correct
B) expression of two different alleles alternates from one generation to the next.
C) a heterozygote expresses an intermediate phenotype.
D) offspring exhibit several different phenotypic expressions of a single trait
A man who carries a harmful sex-linked (on the X chromosome) gene will pass the gene on to
A) all of his daughters. – Correct
B) half of his daughters.
C) half of his sons.
D) all of his sons.
E) all of his sons and daughters
Human skin color is the result of
A) one pair of genes showing incomplete dominance
C) simple dominance
D) sex-linked recessive inheritance
E) polygenic inheritance – Correct
If the quantities of the four bases in a DNA molecule are measured. we find that
A) A = C and G = T
B) A = G and C = T.
C) T = A and C = G – Correct
D) no two bases are equal in amount
E) all bases are equal in amount
Complementary base pairs are held together by
A) peptide bonds
B) hydrogen bonds. – Correct
C) disulfide bonds.
D) covalent bonds.
E) ionic bonds
If the DNA sequence is G-C-C-T- A-T in one polynucleotide chain, then the sequence found polynucleotide chain must be
A) C-G-G-A-T-A. – Correct
_______ replication is the process when DNA uses one parental strand and synthesizes a new strand, resulting in each daughter cell having a new and parental DNA strand.
B) Semiconservative – Correct
The process of copying genetic information from DNA to RNA is called
D) transcription. – Correct
If the sequence of bases in a section of DNA is TAGGCTAA, what is the corresponding sequence of bases in mRNA?
E) AUCCGAUU – Correct
How many bases are in a codon?
A) 3 – Correct
A) is a nucleic acid that carries the code for the primary structure of a protein
B) brings amino acids to the ribosome – Correct
C) is a subunit of ribosomes
D) transfers proteins into the nucleus
What is the anticodon for AUC
E) UAG – Correct
The process of converting the “message” of mRNA into a sequence of amino acids is called
A) translation – Correct
The site of protein synthesis in the cytoplasm is the ribosome
A) True – Correct
Which of the following results from inserting foreign DNA into an organism to produce a new gene combination,
A) Recombinant DNA – Correct
B) Regulatory genes
An organism that contains foreign DNA, which was inserted into its own genetic material, is called
A) transgenic – Correct
A) noncircular DNA segments found only in bacteria
B) small, replicating rings of DNA found in bacteria – Correct
C) chromosomal loops made of RNA
D) found only in three species of bacteria.
The enzymes used to cut genes in recombinant DNA research are called
A) DNA polymerases.
B) RNA polymerases.
D) restriction enzymes. – Correct
In recombinant DNA technology, plasmids
A) are used to insert foreign DNA into bacteria. – Correct
B) show restriction enzymes where to cut bacterial DNA.
C) are necessary for cellular respiration in certain plants.
D) are the sites of protein synthesis in bacteria.
DNA recombination changes the genetic makeup of organisms.
A) True – Correct
Sexual reproduction in humans is an example of DNA recombination.
A) True – Correct
What is the best description of the structure of a chromosome in the nucleus of a non-dividing cell?
One long DNA molecule, associated with many proteins.
What effect does phosphorylating a protein have on that protein?
Phosphorylation changes the shape of the protein, most often activating it.
A human bone marrow cell, in prophase of mitosis, contains 46 chromosomes. How many chromatids does it contain?
Eukaryotic chromosomes are composed of which of the following macromolecules?
DNA and proteins
During _____ both the contents of the nucleus and the cytoplasm are divided.
the mitotic phase
During _____ the cell grows and replicates both its organelles and its chromosomes.
Which of the following is true of kinetochores?
They are sites at which microtubules attach to chromosomes.
Which of the following correctly matches a phase of the cell cycle with its description?
G1: follows cell division
Cytochalasin B is a chemical that disrupts microfilament formation. How would this interfere with cell division?
What is the name of the microtubule-organizing center found in animal cells as an identifiable structure present during all phases of the cell cycle?
In the cells of many eukaryotic species, the nuclear envelope has to disappear to permit which of the following events in the cell cycle?
attachment of microtubules to kinetochores
The mitotic spindle plays a critical role in which of the following processes?
separation of sister chromatids
Metaphase is characterized by ________.
alignment of chromosomes on the equator of the cell
How is plant cell cytokinesis different from animal cell cytokinesis?
Plant cells deposit vesicles containing cell wall building blocks on the metaphase plate; animal cells form a cleavage furrow
Taxol is an anticancer drug extracted from the Pacific yew tree. In animal cells, Taxol prevents microtubule depolymerization. Thus, Taxol stops mitosis by interfering with which of the following structures or processes?
the mitotic spindle
If the cell whose nuclear material is shown in the figure continues toward completion of mitosis, which of the following events would occur next?
formation of telophase nuclei
The drug cytochalasin B blocks the function of actin. Which of the following aspects of the animal cell cycle would be most disrupted by cytochalasin B?
cleavage furrow formation and cytokinesis
Which of the following is true of benign tumors, but not malignant tumors?
They remain confined to their original site
Why do neurons and some other specialized cells divide infrequently?
They have entered into G0.
The M phase checkpoint ensures that all chromosomes are attached to the mitotic spindle. If this does not happen, cells would most likely be arrested in ________.
For a chemotherapeutic drug to be useful for treating cancer cells, which of the following characteristics is most desirable?
It specifically inhibits rapidly dividing cells.
Through a microscope, you can see a cell plate beginning to develop across the middle of a cell and nuclei forming on either side of the cell plate. This cell is most likely
a plant cell in the process of cytokinesis
Vinblastine is a standard chemotherapeutic drug used to treat cancer. Because it interferes with the assembly of microtubules, its effectiveness must be related to
disruption of mitotic spindle formation
One difference between cancer cells and normal cells is that cancer cells
continue to divide even when they are tightly packed together
What is true of all cancers?
They have escaped normal cell cycle controls
How do cancer cells differ from normal cells?
Cancer cells may be immortal.
understanding cell division requires knowledge about
information that guides inheritance, how information in a parent cell is copied, mechanisms that distribute information to daughter cells, and mechanisms that insure new individuals receive parental information
mitosis and cytoplasmic division function in
growth, repair of damaged tissue, replacement of worn-out cells, and asexual reproduction
chromatids that are attached at the centromere are called what kind of chromatids
chromosomes become visible during prophase of mitosis as a result of
chromosomes and genes are replicated during
chromosomes are duplicated during of what portion of the cell cycle
the stage just preceding nuclear and cytoplasmic division is the
in mitosis, if a parent cell has 16 chromosomes, each daughter cell will have how many chromosomes
if a parent cell has 16 chromosomes, how many sister chromatids will be presented after duplication of the chromosomes
cells with two of each kind of chromosome are described by the term
the spindle apparatus is made of
the spindle apparatus begins to become visible during
the chromosomes arrive at opposite poles during
the nuclear membrane re-forms during
a cancer-producing chemical is a(n)
duplicated chromosomes linked together at there centromeres at the beginning of meiosis are appropriately called what kind of chromatids
crossing over occurs during
which of the following will NOT develop into one or more gametes
attached at their centromeres and are identical until crossing over occurs
which of the following does NOT occur in prophase 1 during meiosis
roses have a fossil record dating back to ___ years
in Mendel’s time, most people believed that
the characteristics of parents were blended in the offspring
which of the following genotypes is homozygous
the most accurate description of an organism with genotype AaBb is
Mendel’s theory of independent assortments states that
each hereditary unit is inherited separately from other hereditary units
the “father” of genetics was
true-breeding pea plants always
produce offspring each of which can have only one form of a trait
the difference between a monohybrid cross and a dihybrid cross is that
monohybrid crosses involve one treat; dihybrid traits involve two traits
which of the following statements is true
Darwin did not know what mechanisms were responsible for the variation he saw
the pea plant was an excellent choice for Mendel’s experiments because
true-breeding varieties were available, the pea plant can self-fertilize, and it can be cross-fertilized
which of the following in NOT a characteristic of the pea plants with which Mendel worked
the exhibit blending inheritance
various forms of a gene at a given locus are called
have corresponding alleles on homologous chromosomes, are usually the result of the fusion of two haploid gametes, have two sets of chromosomes, and have pairs of homologous chromosomes
which organism did Mendel utilize to work our the laws of segregation and independent assortment
the garden pea
which of the following statements about Mendel is FALSE
his work was widely recognized even though it did not produce as much controversy as Darwin’s work
if short hair (L) is dominate to long hair (l), animals LL and Ll have the same
if all offspring of a cross have the genotype Aa, the parents of the cross are most likely
AA x aa
an individual with a genetic makeup of aa BB is said to be
who proposed the law of independent assortment
in his experiments with plants, Mendel removed which part of the plant to prevent unwanted fertilizations
a gene locus is
the location of an allele on a chromosome
Mendel’s study of genetics differed from his contemporaries’ studies because he
kept careful records and analyzed the data statistically
in a punnet square, the letters within the little boxes represent
During which phase of mitosis do the sister chromatids separate?
During which phase of mitosis do the nuclear envelopes reform?
During which phase of mitosis do the chromosomes line up in the center of the cell?
During which phase of mitosis do the chromosomes condense?
How many daughter cells does meiosis produce?
What is a difference between mitosis and meiosis?
In meiosis, you cross over twice. In mitosis, you cross over once
During which phase does crossing over occur?
What is it called when two sister chromatids exchange parts?
The gene map shows the relative locations of genes on chromosome 2 of the fruit fly. Between which two genes is crossing over least likely to occur?
Light eye and purple eye (the closer they are together.)
Which phase of meiosis is shown?
Mitosis is used to make gametes.
There are usually 46 chromosomes in a human _______ cell.
Gametes carry only one copy of each chromosome.
All cells in your body undergo meiosis.
Diploid cells have two sets of chromosomes.
Describe binary fission in prokaryotic cells. What must occur before any cell can divide?
Binary fission is the method unicellular organisms such as bacteria(prokaryotes) use for reproduction. This form of reproduction is asexual. It produces offspring genetically identical to the parent organism and can occur very quickly. Before binary fission can begin, DNA must be copied. Once that happens, the cell splits into two new cells.
What is the purpose of cell division in eukaryotic multicellular organisms?
The purpose of cell division in multicellular organisms is to grow, repair, and maintain.
What are the four purposes of cell division in multicellular organisms?
3. Repair of damaged tissues
4. Replacement of lost tissues
What is apoptosis? Why is it important in development and in the prevention of cancer?
Apoptosis is programmed cell death. There are three major check points during the cell cycle in which mitosis will not proceed or the cell will die. Cell death is often associated with faulty or damaged DNA. If the cell would continue to reproduce, the damaged DNA would continue to spread and cancer would develop in the organism.
Briefly describe the cell cycle using the terms interphase, mitosis, and cytokinesis. Do all cells in the human body complete the cell cycle and undergo mitosis and cytokinesis? Give an example of a human cell that does complete the cell cycle and one that does not complete the cell cycle.
The interphase continuum of stages, G1, S, and G2, begins the process in which the cell grows and matures (G1), followed by the S phase in which the DNA is copied. Finally, the G2 phase is when the cell prepares for division. Mitosis occurs when the nucleus of the cell divides into two identical nuclei with the same number and type of chromosomes, followed by cytokinesis when the cytoplasm, for both plant and animal cells, divides, thus creating two daughter cells that are genetically equal and approximately identical in size. Not all cells in the human body complete the cell cycle, such as differentiated neurons and muscle cells that comprise the brain, heart and skeletal muscle. Cells such as skin cells do complete the cell cycle.
What is the definition of mitosis?
Mitosis is the process by which a cell, which has previously replicated each of its chromosomes, separates the chromosomes in its cell nucleus into two identical sets of chromosomes, each set in its own new nucleus.
Describe the events of prophase by describing what happens to the nuclear membrane, nucleolus, chromatin, centrioles, and spindle.
In prophase, chromatin shorten, thicken, and condense into distinct bodies called chromosomes. The nuclear membrane disassembles and the nucleolus is no longer visible. The spindle forms between the centrioles. Centrosome is a pair of centrioles. Duplicated chromosomes begin migrating toward the center of the spindle.
Describe the structure of a duplicated chromosome using the words chromatid and centromere.
Duplicated chromosomes exist as pairs of sister chromatids joined together by a centromere.
What happens to the duplicated chromosome during metaphase? What is the relationship of the hereditary material on either side of the equator?
Duplicated chromosomes are lined up in the center of equator of the spindle during metaphase. The hereditary material is identical on either side of the equator.
What happens during anaphase?
Duplicated chromosomes separate at the centromere and are pulled by the spindle fibers toward each pole. Each single body is now called a chromosome. Cytokinesis begins at the end of anaphase.
What events occur during telophase?
Single chromosomes are at the poles of the spindle. The spindle disassembles and the nuclear membrane and nucleolus reappear. Cytokinesis continues until two daughter cells result.
What is cytokinesis? During which mitotic phase does cytokinesis begin? When is it completed?
Cytokinesis is the process the cytoplasm of a single eukaryotic cell is divided to form two daughter cells. It begins during anaphase and is completed at the end of telophase.
What is the difference between cytokinesis in plant and animal cells? Name the structures that complete cytokinesis in both plant and animal cells.
Animal cells divide by a cleavage furrow. Plant cells divide by a cell plate that eventually becomes the cell wall. Cytoplasm and cell membranes are necessary for cytokinesis in both plants and animals.
In what other way is plant and animal cell mitosis different?
Plant cells do not have centrioles or asters.
What is meiosis? Where and when does it occur? What are the results of meiosis?
Meiosis reduces the chromosome number and is a specialized process because it only produces haploid gametes. And meiosis only occurs in gonads and only occurs after sexual maturation (puberty). Meiosis turns diploids into haploids.
Distinguish between diploid body or somatic cells and haploid gametes or sex cells.
All our body (somatic) cells have 2 copies of each chromosome… and are diploid. Because they contain all 46 chromosomes of the DNA, these Somatic cells are called diploid . On the other hand, Haploid gametes contain only half of the full number of chromosomes . They are produced by sex cells, either ovum or sperm.
Describe the events occurring during meiosis I. What are homologous chromosomes?
The first cell division in Meiosis is known as Meiosis IIn Meiosis I members of homologous chromosome pairs are separated. This results in the segregation of genes into the two gametes. Homologous chromosomes are chromosomes that are matching but not identical. One homologous chromosome is inherited from the organism’s mother; the other from the organism’s father. They are usually not identical, but carry the same type of information.
What is crossing over and when does it occur? What is the significance of crossing over to genetic variability in a sexually reproducing population?
Crossing over occurs during synapsis and are cross-connections that form from breakage and rejoining between sister chromatids occurs between non sister chromatids, where one chromatid is from the mother and one is from the father (makes one pair of homologous). The crossing over is the shuffling of genetic information and the recombination of it, which allows for genetic variability in families with the same parents.
What is the result of meiosis I in terms of cell number and chromosome number and arrangement?
The chromosome number is cut in half as a result of meiosis I and two haploid cells are produced. Each cell pole has a cluster of chromosomes that corresponds to a complete haploid set, one member of each homologous chromosome pair at the end of meiosis I,.
In humans, how many different ways can the 23 homologous pairs of chromosomes line up at the metaphase plate or equator during metaphase I?
What is interkinesis? Does the DNA replicate during interkinesis?
It is the period of time between meiosis I and meiosis II. There is no replication of DNA in this stage.
Describe the events of meiosis II. What results after completion of meiosis II?
Once both cell poles have a haploid set of chromosomes clustered around them, these chromosomes divide mitotically (without reshuffling or reducing the number of chromosomes during division) during the second part of meiosis. This time, the spindle fibers bind to both faces of the kinetochore, the centromeres divide, and the sister chromatids move to opposite cell poles. At the end of meiosis II, therefore, the cell has produced four haploid groups of chromosomes. Nuclear envelopes are formed around each of these four sets of chromosomes, and the cytoplasm is physically divided among the four daughter cells in a process known as cytokinesis.
What is gametogenesis? What is spermatogenesis? Are all four cells resulting from spermatogenesis viable as gametes?
Gametogenesis is the production of gametes, or sex cells, and is the process of meiosis. Spermatogenesis is the name for gametogenesis in males. All four resulting cells from spermatogenesis are viable as gametes.
What is oogenesis? Why does one secondary oocyte get the majority of the cytoplasm, resulting in three useless polar bodies?
Oogenesis is the name for gametogenesis in females. If all four oocytes survived, it would be very possible for all women to have four babies at a time, which the body is not constructed for.
What is a zygote? What is the number of chromosomes in a human zygote? and what type of cell division results in the multicellular fetus, child, and adult?
A zygote is a fertilized egg. A human zygote contains 46 chromosomes because it is the combination of two gametes. Mitosis occurs throughout the human life.
What is meant by reduction division in describing meiosis and gametogenesis?
Meiosis reduces the number of chromosomes and divides it in half from that of a normal cell, such as a skin cell.
Describe how both mitosis and meiosis are necessary in the human life cycle.
It is very essential that cells go through mitosis so that each new cell contains the same gentic information. It is also very essential that meiosis occurs because reproduction would cease.
Genomic DNA is replicated during which of the following cell-cycle phases?
S – Correct
Cells grow primarily during which of the following cell-cycle phases?
G1 – Correct
Dividing adult eukaryotic cells spend most of their time in which of the following?
interphase – Correct
Which of the following correctly orders the stages of mitosis?
a. prometaphase – metaphase – anaphase – prophase – telophase
b. telophase – prometaphase – prophase – metaphase – anaphase
c. prophase – prometaphase – metaphase – anaphase – telophase – Correct
d. anaphase – prometaphase – metaphase – prophase – telophase
e. prophase – anaphase – prometaphase – metaphase – telophase
The cell-cycle phase that varies most in duration in various eukaryotic adult cell types is
G1. – Correct
Chromosome condensation indicates a cell has entered
prometaphase. – Correct
Animal cell centrosome MTOCs contain
centrioles. – Correct
Which of the following recruits proteins to form a kinetochore at the centromere?
CENP-A – Correct
Each of the following is an activity of a microtubule motor protein during mitosis except
pulling astral microtubules toward the cell cortex.
shortening kinetochore microtubules.
pushing interpolar microtubules for anaphase B.
pulling kinetochore microtubules in at centrosomes.
All of the above are activities of microtubule motors. – Correct
Which of the following occurs during prometaphase (late prophase)?
continuous kinetochore microtubule shortening
APC targeting of securin destruction
Rho-stimulated formation of a contractile ring
nuclear envelope fragmentation – Correct
A mutant cell in which sister chromatids get torn apart rather than separating correctly at anaphase most likely is deficient in
topoisomerase II. – Correct
Each of the following is true about anaphase except
during anaphase A, each chromosome is pulled to its respective pole as its kinetochore microtubules shorten.
during anaphase B, the spindle poles are pushed further apart as interpolar microtubules lengthen.
anaphase B may be coincident with or follow anaphase A, depending on the cell type.
anaphase is the shortest stage of the mitosis.
All of the above are true. – Correct
The appearance that the spindle and sister chromatids are inactive at metaphase is misleading because
each sister chromatid is being pulled toward its respective pole. – Correct
the sister chromatids are decondensing.
the sister chromatids are signaling reformation of the nuclear envelope.
each sister chromatid is assembling a kinetochore.
the sister chromatids are completing replication at numerous replicons.
Each of the following provides evidence that kinetochore microtubule shortening is directly involved in anaphase A chromosome movement to a pole except
a. Stabilization of microtubules with the drug paclitaxel stops chromosome movement to a pole.
b. Laser bleaching of labeled kinetochore microtubules indicates they shorten at the kinetochore as the chromosome moves toward a pole.
c. Treatment that accelerates microtubule depolymerization causes chromosomes to move toward the poles more quickly.
d. Antibody inhibition of kinesin depolymerization of kinetochore microtubules interferes with chromosome movement to a pole.
e. All of the above are evidence that kinetochore microtubule shortening is directly involved in anaphase A chromosome movement to a pole. – Correct
Each of the following is involved in plants cell cytokinesis except
a. assembly of vesicle noncellulose components to form the primary cell wall.
b. phragmoplast alignment of Golgi-derived vesicles in the center of the dividing cell.
c. abscission of the cell into two cells. – Correct
d. fusion of Golgi-derived vesicles to form the cell plate.
e. All of the above are correct.
Phosphorylation of ________ is directly required for chromosome condensation.
condensin – Correct
The multiple sites of DNA replication along eukaryotic chromosomes are known as
targets of rapamycin.
replicons. – Correct
Mitotic Cdk-cyclin is active when it is
singly phosphorylated. – Correct
cleaved by proteases.
Cyclins modulate the progression of cells through the cell cycle by directly
activating G proteins.
activating protein kinases that are critical regulators of cell division. – Correct
turning on genes necessary for DNA replication.
phosphorylating growth factor receptors.
A eukaryotic cell G2-M checkpoint assesses the status of
the presence of growth factors.
mitotic cyclin degradation.
chromosome attachment to kinetochore microtubules.
DNA replication. – Correct
In the cell cycle, controlled degradation of regulatory proteins occurs via the
ubiquitin-proteasome pathway. – Correct
kinase inhibition pathway.
In the cell cycle, a mitotic Cdk is present during
All of the above phases. – Correct
Each of the following involves apoptosis except
removing webbing between digits during development.
generating a cancerous tumor. – Correct
destroying pathogen-infected cells.
decreasing neurons during brain development.
removing white blood cells at the end of their lifespan.
Alternative forms of a gene are known as
alleles. – Correct
Which of the following is true about mitosis or meiosis?
Homologues separat in prophase I of meiosis.
Sister chromatids separate in prophase I of meiosis.
Homologues separate in prophase II of meiosis .
Homologues are separated in prophase of mitosis.
Sister chromatids are separated in anaphase II of meiosis. – Correct
How many chromatids are present in prophase I in a diploid cell in which 2n = 12?
24 – Correct
Can’t tell – more information is required.
What is the distribution of parental chromosomes in each of the four haploid cells produced by meiosis II?
a. a 75%:25% mix of maternal and paternal chromosomes
b. a 50%:50% mix of maternal and paternal chromosomes
c. 100% maternal or paternal chromosomes
d. a random mix of maternal and paternal chromosomes – Correct
e. The distribution depends on whether the organism is haploid or diploid.
Meiosis I results in the formation of
two haploid cells. – Correct
one quadraploid cell.
two diploid cells.
four haploid cells.
four diploid cells.
Which of the following types of organisms is always haploid?
bacteria – Correct
Meiosis most resembles mitosis in
a. the phases of meiosis I.
b. meiosis I, except for the pairing of homologues.
c. meiosis II, except for the pairing of homologues.
d. the phases of meiosis II. – Correct
e. all phases of meiosis I and meiosis II.
a. two rounds of chromosomal replication and two nuclear divisions.
b. one round of chromosomal replication and two nuclear divisions. – Correct
c. two rounds of chromosomal replication and one nuclear division.
d. one round of chromosomal replication and one nuclear division.
e. the number of rounds of chromosomal replication and nuclear divisions depends on whether the cell is haploid or diploid.
Homologous chromosomes are held together by
a synaptonemal complex. – Correct
What are some genetic differences between prokaryotic and eukaryotic cells?
No paired chromosomes (haploid)
Typically single circular chromosome containing a single origin of replication
Single chromosome is replicated with each copy moving to opposite sides of the cell
No histone proteins bound to DNA
Paired chromosomes common (diploid)
Typically multiple linear chromosomes containing centromeres, telomeres, and multiple origins of replication
Chromosomes are replicated and segregate during mitosis or meiosis to the proper location
Histone proteins are bound to DNA
Outline the process by which prokaryotic cells reproduce.
(1) Replication of the circular chromosome takes place.
(2) The two replicated chromosomal copies attach to the plasma membrane.
(3) The plasma membrane grows, which results in the separation of the two chromosomes.
(4) A new cell wall is formed between the two chromosomes that produces two cells, each with its own chromosome.
Name three essential structural elements of a functional eukaryotic chromosome and describe their functions.
(1) Centromere: serves as the point of attachment for the kinetochore to which spindle fibers (microtubules) attach
(2) Telomeres, or the natural ends of the linear eukaryotic chromosome: serve to stabilize the ends of the chromosome; may have a role in limiting cell division
(3) Origins of replication: serve as the starting place for DNA synthesis
Sketch and identify four different types of chromosomes based on the position of the centromere.
metacentric submetacentric acrocentric telocentric
What are checkpoints? List some of the important checkpoints in the cell cycle.
List the stages of mitosis and the major events that take place in each stage.
(1) Prophase: The chromosomes condense and become visible, the centrosomes move apart, and microtubule fibers form from the centrosomes.
(2) Prometaphase: The nucleoli disappear and the nuclear envelope begins to disintegrate, allowing for the cytoplasm and nucleoplasm to join. The sister chromatids of each chromosome are attached to microtubules from the opposite centrosomes.
(3) Metaphase: The spindle microtubules are clearly visible and the chromosomes arrange themselves on the equatorial plane of the cell.
(4) Anaphase: The sister chromatids separate at the centromeres after the breakdown of cohesin protein, and the newly formed daughter chromosomes move to the opposite poles of the cell.
(5) Telophase: The nuclear envelope reforms around each set of daughter chromosomes. Nucleoli reappear. Spindle microtubules disintegrate.
Briefly describe how the chromosomes move toward the spindle poles during anaphase.
Due to the actions of the microtubule subunits attached to the kinetochores of the chromosome and motor proteins e.g., the protein kinesin is a motor protein, the chromosomes are pulled toward the spindle poles during anaphase. The spindle fibers are composed of tubulin protein subunits. As the tubulin subunits are removed from the – end of the microtubule, the chromosome is pulled or reeled in toward the spindle pole as the microtubule is shortened. While at the + end, the kinetochore is removing tubulin subunits of the microtubule attached to the kinetochore with the net effect being the movement of the chromosome closer to the spindle pole. Molecular motor proteins, such as kinesin, are responsible for removing the subunits at the + and – ends of the microtubules and thus generate the force needed to move the chromosomes.
What are the genetically important results of the cell cycle and mitosis?
In the mitotic cell cycle, the genetic material is precisely copied and mitosis ensures that the identical copies of the genetic material are separated accurately into the new daughter cells, resulting in two cells containing the same genetic information. In other words, the cells have genomes identical to each other and to the mother cell.
Why are the two cells produced by the cell cycle genetically identical?
In the S phase an exact copy of each DNA molecule was created that is why the two cells are genetically identical. These exact copies give rise to the two identical sister chromatids. Mitosis ensures that each new cell receives one of the two identical sister chromatids. Thus, the newly formed cells will contain identical daughter chromosomes
What are the stages of meiosis and what major events take place in each stage?
Meiosis I: Separation of homologous chromosomes
Prophase I: The chromosomes condense and homologous pairs of chromosomes undergo synapsis. While the chromosomes are synapsed, crossing over occurs. The nuclear membrane disintegrates and the meiotic spindle begins to form.
Metaphase I: The homologous pairs of chromosomes line up on the equatorial plane of the metaphase plate.
Anaphase I: Homologous chromosomes separate and move to opposite poles of the cell. Each chromosome possesses two sister chromatids.
Telophase I: The separated homologous chromosomes reach the spindle poles and are at opposite ends of the cell.
Cytokinesis follows Meiosis I , whch results in the division of the cytoplasm and the production of two haploid cells. These cells may skip directly into meiosis II or enter interkinesis, where the nuclear envelope reforms and the spindle fibers break down.
Meiosis II: Separation of sister chromatids
Prophase II: Chromosomes condense, the nuclear envelope breaks down, and the spindle fibers form.
Metaphase II: Chromosomes line up at the equatorial plane of the metaphase plate.
Anaphase II: The centromeres split, which results in the separation of sister chromatids.
Telophase II: The daughter chromosomes arrive at the poles of the spindle. The nuclear envelope reforms, and the spindle fibers break down.
Following meiosis II, cytokinesis takes place.
What two processes unique to meiosis are responsible for genetic variation? At what point in meiosis do these processes take place?
(1) Crossing over, which begins during the zygotene stage of prophase I and is completed near the end of prophase I.
(2) The random distribution of separated members of the homologous chromosomes (the maternal and paternal chromosomes) to daughter cells, which takes place in anaphase I of meiosis. in metaphase I, the separation arrangement is determined by the random alignment of homologs.
A cell in G1 of interphase has 12 chromosomes. How many chromosomes and DNA molecules will be found per cell when this original cell progresses to the following stages?
a. G2 of interphase
G2 of interphase occurs after S phase, when the DNA molecules are replicated. Each chromosome now consists of two DNA molecules. So a cell in G2 will contain 12 chromosomes and 24 DNA molecules.
b. Metaphase I of meiosis
Neither homologous chromosomes nor sister chromatids have separated by metaphase I of meiosis. Therefore, the chromosome number is 12, and the number of DNA molecules is 24.
c. Prophase of mitosis
This cell will contain 12 chromosomes and 24 DNA molecules.
d. Anaphase I of meiosis
During anaphase I of meiosis, homologous chromosomes separate and begin moving to opposite ends of the cell. However, sister chromatids will not separate until anaphase II of meiosis. The number of chromosomes is still 12, and the number of DNA molecules is 24.
e. Anaphase II of meiosis
At the completion of meiosis I, Homologous chromosomes were separated and migrated to different daughter cells . However, in anaphase II of meiosis, sister chromatids separate, resulting in a temporary doubling of the chromosome number in the now haploid daughter cell. The number of chromosomes and the number of DNA molecules present will both be 12.
f. Prophase II of meiosis
The daughter cells in prophase II of meiosis are haploid. The haploid cells will contain six chromosomes and 12 DNA molecules.
g. After cytokinesis following mitosis
After cytokinesis following mitosis the daughter cells will enter G1. Each cell will contain 12 chromosomes and 12 DNA molecules.
h. After cytokinesis following meiosis II
After cytokinesis following meiosis II, the haploid daughter cells will contain six chromosomes and six DNA molecules.
The cell cycle
All of the following statements are true except
A) Mitosis produces new nuclei with exactly the same chromosomal endowment as the parent nucleurs.
B) Mitosis may occur without cytokinesis.the
C) Mitosis and cytokinesis are requirments for asexual reproduction.
D) All cells come from a preexisting cell.
E) The mitotic spindles in prokaryotic cells are composed of microtubules. – Correct
The centromere is a region in which
A) chromatids are attached to one another. – Correct
B) metaphase chromosomes become aligned
C) chromosomes are grouped during telophase.
D) the nucleus is located prior to mitosis E) new spindle microtubules form.
At metaphase of mitosis
A possible daughter cell of mitosis
Two centrosomes are arranged at opposite poles of the cell.
Centrioles begin to move apart in animal cells.
Centromeres uncouple, sister chromatids are separated, and the two new chromosomes move to opposite poles of the cell
If cells in the process of dividing are subjected to colchicine, a drug that interferes with the functioning of the spindle apparatus, at which stage will mitosis be arrested?
D) metaphase – Correct
A cell completion, produce two nuclei metaphase of mitosis would, at its containing 92 chromatids at containing how many chromosomes?
D)46 – Correct
If the cell whose nuclear material is show in Figure 12.2 continues toward completion of mitosis, which of the following events would occur next?
A) cell membrane synthesis
B) spindle fiber formation
C) nuclear envelope breakdown
D)formation of telophase nuclei – Correct
E) synthesis of chromatids
All of the following occur during prometaphase of mitosis in animal cells except
A) the centrioles move toward opposite poles
B) the nucleolus can no longer be seen. C) the nuclear envelope disappears
D) chromosomes are duplicated – Correct
E) the spindle is organized.
If there are 20 centromeres in a cell, how many chromosomes are there?
B) 20 – Correct
Of the following, the best conclusion concerning the difference between the S phases for beta and gamma is that
A) gamma contains more DNA than beta. – Correct
B) beta and gamma contain the same amount of DNA.
C) beta contains more RNA than gamma.
D) gamma contains 48 times more DNA and RNA than beta.
E) beta is a plant cell and gamma is an animal cell.
The best conclusion concerning delta is that the cells
A) contain no DNA.
B) contain no RNA.
C) contain only one chromosome that is very short.
D) are actually in the Go phase. – Correct
E) divide in the G1 phase.
The S phase was measured by
A) counting the number of cells.
B) determining the start and stop of increased DNA in the cells. protein. – Correct
C) synthesis versus breakdown of S
D) synthesis of the S chromosome.
E) stopping G1
Where do the microtubules of the spindle originate during mitosis in both plant and animal cells?
B) centrosome – Correct
All of the following occur during mitosis except
A) the condensing of chromosomes.
B) the uncoupling of chromatids at the centromere.
C) the formation of a spindle.
D) the synthesis of DNA. – Correct
E) the disappearance of the nucleolus.
If a cell has 8 chromosomes at metaphase of mitosis, how many chromosomes will it have during anaphase?
E) 16 – Correct
Cytokinesis usually, but not always follows mitosis. If a cell completed mitosis but not cytokinesis, what would be the result?
A) a cell with a single large nucleus
B) a cell with high concentrations of actin and m yosin
C) a cell with two abnormally small nuclei
D) a cell with two nuclei – Correct
E) a cell with two nuclei but with half the amount of DNA
Regarding mitosis and cytokinesis, one difference between higher plants and animals is that in plants
A) the spindles contain microfibrils in addition to microtubules, whereas animal spindles do not contain microfibrils.
B) sister chromatids are identical, but they differ from one another in animals.
C) a cell plate begins to form at telophase, whereas in animals a cleavage furrow is initiated at that stage. – Correct
D) chromosomes become attached to the spindle at prophase, whereas in animals chromosomes do not become attached until anaphase.
E) spindle poles contain centrioles, whereas spindle poles in animals do not.
How do the daughter cells at the end of mitosis and cytokinesis compare with their parent cell when it was in G1 of the cell cycle?
A) The daughter cells have half the amount of cytoplasm and half the amount of DNA.
B) The daughter cells have half the number of chromosomes and half the amount of DNA.
C) The daughter cells have the same number of chromosomes and half the amount of DNA.
D) The daughter cells have the same number of chromosomes and the same amount of DNA. – Correct
E) The daughter cells have the same number of chromosomes and twice the amount of DNA.
The formation of a cell plate is beginning across the middle of a cell and nuclei are re-forming at opposite ends of the cell. What kind of cell is this?
A) an animal cell in metaphase
B) an animal cell in telophase
C) an animal cell undergoing cytokinesis
D)a plant cell in metaphase
E)a plant cell undergoing cytokinesils – Correct
Taxol is an anticancer drug extracted from the Pacific yew tree. In animal cells, taxol disrupts microtubule formation by binding to microtubules and accelerating their assembly from the protein precursor, tubulin. Surprisingly, this stops mitosis. Specifically, taxol must affect
A) the fibers of the mitotic spindle. – Correct
C) formation of the centrioles.
D) chromatid assembly
E) the S phase of the cell cycle.
Which of the following is (are) primarily responsible for cytokinesis in plant cells?
B) Golgi-derived vesicles – Correct
C) actin and myosin
D) centrioles and basal bodies
E) cyclin-dependent kinases
Which of the following organisms does not reproduce cells by mitosis and cytokinesis?
B) bacterium – Correct
E) banana tree
During which phase(s) of mitosis do we find chromosomes composed of two chromatids?
A) from interphase through anaphase
B) from G1 of interphase through metaphase
C) from metaphase through telophase D) from anaphase through telophase
E) from G2 of interphase through metaphase – Correct
Which of the following is not true of the bacterial chromosome?
A) It consists of a single, circular DNA molecule
B) DNA replication begins at the origin of replication
C)Its centromeres uncouple during replication – Correct
D) It is highly folded within the cell.
E) It has genes that control binary fission.
In which group of eukaryotic organisms does the nuclear envelope remain intact during mitosis?
A) seedless plants
D) B and C – Correct
E) A, B, and C
Movement of the chromosomes during anaphase would be most affected by a drug that
A) reduced cyclin concentrations.
B) increased cyclin concentrations.
C) prevented elongation of microtubules.
D) prevented shortening of microtubules. – Correct
E) prevented attachment of the microtubules to the kinetochore.
If mammalian cells receive a go-ahead signal at at the G1 checkpoint, they will
A) move directly into telophase.
B) complete the cycle and divide. – Correct
C) exit the cycle and switch to a nondividing state.
D) show a drop in MPF concentration.
E) complete cytokinesis and form new cell walls.
Cells that are in a nondividing state are in which phase?
A)Go – Correct
Measurements of the amount of DNA per nucleus were taken on a large number of cells from a growing fungus. The measured DNA levels raniged from 3 to 6 picograms per nucleus. In which stage of the cell cycle was the nucleus with 6 picograms of DNA?
D)G2 – Correct
What causes the rhythmic change in cyclin concentration in the cell cycle?
A) an increase in production once the restriction point is passed
B) the cascade of increased production once its protein is phosphorylated by Cdk
C) the changing ratio of cytoplasm to genome
D) its destruction by an enzyme phosphorylated by MPF
E) the binding of PDGF to receptors on the cell surface
released by platelets in the vicinity of an injury
enzymes that activate or inactivate other proteins by phosphorylating them
fibroblasts have receptors for this substance on their plasma membranes
a protein synthesized through the cell cycle that associates with a kinase to form active enzymes
triggers the cell’s passage past the G2 checkpoint into mitosis
The restriction point occurs here.
Nerve and muscle cells are in this phase.
the shortest part of the cell cycle
DNA is replicated at this time of the cell cycle.
Cyclin is destroyed toward the end of this phase.
In the figure above, mitosis is represented by which number?
D)IV – Correct
MPF reaches its threshold concentration at the end of this stage.
A ) I
C ) III – Correct
Which number represents G1
A)I and V – Correct
B ) I and IV
Which number represents DNA synthesis?
B) II – Correct
What are enzymes called that control the activities of other proteins by phosphorylating them?
B) kinases – Correct
E) protein kinases
A group of cells is assayed for DNA content immediately following mitosis and is found to have an average of 8 of DNA per nucleus. Those cells would have… picograms at the end of the S phase and…picograms at the end of G2 A) 8.. 8
B) 8… 16
C) 16… 8
D)16… 16 – Correct
E) 12… 16
As the cell progreses through prophase and into metaphase, what happens to the active anaphase-promoting complex proteins?
A) They increase gradually during telophase.
B) They decrease gradually until it is depleted at metaphase.
C) They increase sharply once all the chromosomes are lined up in metaphase. – Correct
D) They are initially high, but drop precipitously when all the chromosomes are lined up in metaphase.
E) They remain constant from prophase through metaphase.
What triggers the separation of chromatids during mitosis?
A) intemal signals originating at the centromere
B) the activation of proteins holding sister chromatids together
C) the buildup of cyclin near the kinetochores
D) activation of an anaphase-promoting complex (APC) – Correct
E) the release of platelet-derived growth factor from the Golgi
Proteins that are involved in the regulation of the cell cycle, and that show fluctuations in concentration during the cell cycle, are called
D) proton pumps
E) cyclins. – Correct
The MPF protein complex turns itself off by
A) activating an enzyme that destroys cyclin. – Correct
B) activating an enzyme that stimulates cyclin
C) binding to chromatin.
D) exiting the cell.
E) activating the anaphase-promoting complex.
Recent research has indicated that cancer cells
A) transform normal cells by altering genes involved in the control of mitosis – Correct
B) always develop into a tumor
C) contain more than the normal number of chromosomes.
D) are unable to complete the cell cycle after the S phase.
E) enter and exit the Go phase three times before they divide
A mutation results in a cell that no longer produces a normal protein kinase for the M phase checkpoint. Which of the following would likely be the immediate result of this mutation?
A) The cell would prematurely enter anaphase.
B) The cell would never leave metaphase.
C) The cell would never enter metaphase.
D) The cell would never enter prophase
E) The cell would undergo normal mitosis, but fail to enter the next G1 – Correct
Density-dependent inhibition” is explained by which of the following?
A) As cells become more numerous, they begin to squeeze against each other restricting their size and ability to produce control factors.
B) As cells become more numerous, the amount of required growth factors and nutrients per cell becomes insufficient to allow for cell growth. – Correct
C) As cells become more numerous, the protein kinases they produce begin to compete with each other, such that the proteins produced by one cell essentially cancel those produced by its neighbor
D) As cells become more numerous, more and more of them enter the S phase of the cell cycle.
E) As cells become more numerous, the level of waste products increases , eventually slowing down metabolism.
Which of the following is true concerning cancer cells?
A) They do not exhibit density-dependent inhibition when growing in culture.
B) When they stop dividing they do so at random points in the cell cycle
C) They have escaped from cell cycle controls.
D) B and C are true.
E) A, B, and C are true. – Correct
Asexual reproduction requires individual(s).
B)1 – Correct
The genetic material is duplicated during
A) the mitotic phase.
C) the S phase. – Correct
Chromosomes are aligned along the cell ‘s equator during
D) metaphase. – Correct
The absence of a single cell with two nuclei would result in
E) cytokinesis – Correct
is a carcinogen that may promote colon cancer
A) Fat – Correct
B) UV light
D) A virus
During the cell cycle, increases in the enzymatic activity of protein kinases are due to
A) kinase synthesis by ribosomes.
B) activation of inactive kinase by binding to cyclin. – Correct
C) conversion of inactive cyclin to the active kinase by means of phosphorylation.
D) cleavage of the inactive kinase molecules by cytoplasmic proteases
E) a decline in external growth factors to a concentration below the inhibitory threshold.
Through á microscope, you can see a cell plate beginning to develop across the middle of the cell and nuclei re-forming at opposite poles of the cell. This cell is most likely
A)an animal cell in the process of cytokinesis.
B) a plant cell in the process of cytokinesis. – Correct
C) an animal cell in the S phase of the cell cycle
D) a bacterial cell dividing.
E) a plant cell in metaphase.
Vinblastine is a standard cancer. Since it interferes chemotherapeutic drug used to treat with the assembly of microtubules, its effectiveness must be related to
A) disruption of mitotic spindle formation. – Correct
B) inhibition of regulatory protein phosphorylation.
C) suppression of cyclin production.
D) myosin denaturation and inhibition of cleavage furrow formation.
E) inhibition of DNA synthesis.
A particular cell has half as much DNA as some of the other cells in a mitotically active tissue. The cell in question is most likely in
A)G1 – Correct
One difference between a cancer cell and a normal cell is that
A) the cancer cell is unable to synthesize DNA.
B) the cell cycle of the cancer cell is arrested at the S phase.
C) cancer cells continue to divide even when they are tightly packed together. – Correct
D) cancer cells cannot function properly because they suffer from density-dependent inhibition.
E) cancer cells are always in the M phase of the cell cycle.
The decline caused by of MPF at the end of mitosis is
A) the destruction of the protein kinase (Cdk).
B) decreased synthesis of cyclin.
C)the enzymatic destruction of cycdin. – Correct
D) synthesis of DNA.
E) an increase in the cell’s volume-to-genome ratio.
A red blood cell ( RBC ) has a 120 – day life span. If an average adult has 5 L (5,000 cm3) of blood and each cubic millimeter contains 5 million RBCs, how many new cells must be produced each second to replace the entire RBC population?
C) 2,400,000 – Correct
In function, the plant cell structure that is analogous to an animal cell’s cleavage furrow is the
B) cell plate. – Correct
E) spindle apparatus.
In some organisms, mitosis occurs without cytokinesis occurring. This will result in
A) cells with more than one nucleus. – Correct
B) cells that are unusually small.
C) cells lacking nuclei.
D) destruction of chromosomes.
E) cell cycles lacking an S phase.
Which of the following does not occur during mitosis?
A) packaging of the chromosomes
B) replication of the DNA – Correct
C) separation of sister chromatids
D) spindle formation
E) separation of the centrosomes
Four genes (A, B, C, and D) are on the same chromosome. The recombination frequencies are as follows: A-B: 19%; B-C: 14%; A-C: 5%; B-D: 2%; A-D: 21%; C-D: 16%. Based on this information, which sequence of genes is correct?
In Drosophila melanogaster, vestigial wings are determined by a recessive allele of a gene that is linked to a gene with a recessive allele that determines black body color. T. H. Morgan crossed black-bodied, normal-winged females and gray-bodied, vestigial-winged males. The F1 were all gray bodied, normal winged. The F1 females were crossed to homozygous recessive males to produce testcross progeny. Morgan calculated the map distance to be 17 map units. Which of the following information is correct about the testcross progeny?
gray-bodied, normal-winged flies plus black-bodied, vestigial-winged flies = 17% of the total
In general, the frequency with which crossing over occurs between two linked genes depends on what?
how far apart they are on the chromosome
Which of the following occurrences describes how recombination between linked genes comes about?
Crossovers between these genes result in chromosomal exchange.
What does a recombination frequency of 50% indicate?
The two genes are likely to be located on different chromosomes.
Which of these descriptions of the behavior of chromosomes during meiosis explains Mendel’s law of independent assortment?
The arrangement of each pair of homologous chromosomes on the metaphase plate during metaphase I is random with respect to the arrangements of other pairs.
Linkage and mapping genetics
A gray-bodied, vestigial-winged fly is crossed with a black-bodied, normal-winged fly. The F1 progeny is testcrossed. Among the resulting offspring, __________ is a parental type, and __________ is a recombinant type.
black-bodied, normal-winged … black-bodied, vestigial-winged
What name is given to the most common phenotype in a natural population?
Which of the following statements correctly describes the meaning of the chromosome theory of inheritance as expressed in the early 20th century?
Mendelian genes are at specific loci on the chromosome and, in turn, segregate during meiosis
What is an adaptive advantage of recombination between linked genes?
New allele combinations are acted upon by natural selection.
A white-eyed female Drosophila is crossed with a red-eyed male Drosophila. Which statement below correctly describes the results?
none of the females will have white eyes
When Thomas Hunt Morgan crossed his red-eyed F1 generation flies to each other, the F2 generation included both red- and white-eyed flies. Remarkably, all the white-eyed flies were male. What was the explanation for this result?
the gene involved is located on the X chromosome
Which of the following results of Thomas Hunt Morgan’s experiments with white-eyed mutant flies was unexpected in light of Mendelian genetics?
Among the F2 progeny, only males had white eyes. All of the females had red eyes.
Map units on a linkage map cannot be relied upon to calculate physical distances on a chromosome for which of the following reasons?
The frequency of crossing over varies along the length of the chromosome
Which of the following statements correctly describes the reason that closely linked genes are typically inherited together?
They are located close together on the same chromosome.