EXAM 4
B
A cleavage furrow is ________. a. the separation of divided prokaryotes b. a groove in the plasma membrane between daughter nuclei c. the space that is created between two chromatids during anaphase d. a ring of vesicles forming a cell plate
A
If a cell at metaphase of mitosis contains 20 sister chromatids, how many chromosomes will be present in a G1 cell? a. 10 b. 40 c. 20 d. 5
A
In the figure, which number represents DNA synthesis? A. II B. III C. I D. IV
B
Inheritance patterns cannot always be explained by Mendel's models of inheritance. If a pair of homologous chromosomes fails to separate during meiosis I, select the choice that shows the chromosome number of the four resulting gametes with respect to the normal haploid number (n)? A. n + 1; n + 1; n; n B. n + 1; n + 1; n - 1; n - 1 C. n + 1; n - 1; n - 1; n - 1 D. n + 1; n - 1; n; n
C
Measurements of the amount of DNA per nucleus were taken on a large number of cells from a growing fungus. The measured DNA levels ranged from 3 to 6 picograms per nucleus. In which stage of the cell cycle did the nucleus contain 6 picograms of DNA? a. S b. G0 c. G2 d. G1
D
One difference between cancer cells and normal cells is that cancer cells a. are arrested at the S phase of the cell cycle. b. cannot function properly because they are affected by density-dependent inhibition. c. are unable to synthesize DNA. d. continue to divide even when they are tightly packed together.
A
Starting with a fertilized egg (zygote), a series of six cell divisions would produce an early embryo with how many cells? a. 64 b. 32 c. 16 d. 12
B
What two components constitute an active MPF? a. a growth factor and mitotic factor b. cyclin and a cyclin-dependent kinase c. cyclin and tubulin d. ATP synthetase and a protease
D
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? A. The gene involved is located on the Y chromosome. B. The gene involved is located on an autosome, but only in males. C. Other male-specific factors influence eye color in flies. D.The gene involved is located on the X chromosome.
D
Which of the following does not occur during mitosis? a. spindle formation b. condensation of the chromosomes c. separation of sister chromatids d. replication of the DNA
C
Which of the following statements correctly describes the reason that closely linked genes are typically inherited together? A. The number of genes in a cell is greater than the number of chromosomes. B. Alleles are paired together during meiosis. C. They are located close together on the same chromosome. D. Genes align that way during metaphase I of meiosis.
B
Which of the following statements correctly describes what happens to a chromosome after a nonreciprocal translocation occurs? A. A duplication of part of the chromosome occurs. B. A chromosome transfers a fragment but receives none in return. C. Nondisjunction of pairs of homologous occurs. D. A deletion of part of the chromosome occurs.
A
Why do neurons and some other specialized cells divide infrequently? a. They have entered into G0 b. They no longer have active nuclei. c. They no longer produce MPF. d. They can no longer degrade cyclins.
C
5. Vinblastine is a standard chemotherapeutic drug used to treat cancer. Because it interferes with the assembly of microtubules, its effectiveness must be related to a. myosin denaturation and inhibition of cleavage furrow formation. b. suppression of cyclin production. c. disruption of mitotic spindle formation. d. inhibition of DNA synthesis.
B
A certain kind of snail can have a right-handed direction of shell coiling (DD or Dd) or left-handed coiling (dd). However, if direction of coiling is due to a protein deposited by the mother in the egg cytoplasm, then a Dd egg-producing snail and a dd sperm-producing snail will have offspring of which genotype(s) and phenotype(s)? A. 1/2 Dd: 1/2 dd; half right-coiling and half left-coiling B. 1/2 Dd:1/2 dd; all right-coiling C. all Dd; all right-coiling D. all Dd; half right-coiling and half left-coiling
A
A couple has a child with Down syndrome. The mother is 39 years old at the time of delivery. Which of the following is the most probable cause of the child's condition? A. One of the gametes in the mother most likely underwent nondisjunction during meiosis. B. The mother had a chromosomal duplication. C. One member of the couple underwent nondisjunction in somatic cell production. D. The woman inherited this tendency from her parents.
B
A group of cells is assayed for DNA content immediately following mitosis and is found to have an average of 8 picograms of DNA per nucleus. How many picograms of DNA would be found in a nucleus at prophase of mitosis? a. 4 b. 16 c. 24 d. 8
A
A homozygous tomato plant with red fruit and yellow flowers was crossed with a homozygous tomato plant with golden fruit and white flowers. The F1 all had red fruit and yellow flowers. The F1 were testcrossed by crossing them to homozygous recessive individuals, and the following offspring were obtained: Red fruit and yellow flowers—41 Red fruit and white flowers—7 Golden fruit and yellow flowers—8 Golden fruit and white flowers—44 How many map units separate these genes? A. 15 B. 17.6 C. 18.1 D. 17.1
B
A man who is a dwarf with achondroplasia and normal vision marries a color-blind woman of normal height. The man's father was six feet tall, and both the woman's parents were of average height. Dwarfism caused by achondroplasia is autosomal dominant, and red-green color blindness is X-linked recessive. How many of their daughters might be expected to be color-blind with achondroplasia? A. half B. none C. three out of four D. one out of four
D
A phenotypically normal prospective couple seeks genetic counseling because the man knows that he has a translocation of a portion of his chromosome 4, which has been exchanged with a portion of his chromosome 12. Although his translocation is balanced, he and his wife want to know the probability that his sperm will be abnormal. What is your prognosis regarding his sperm? A. Half will be normal, and the rest will have the father's translocation B. None will carry the translocation C. All will carry the same translocation as the father D. One-quarter will carry the two normal chromosomes, 4 and 12, one-quarter will have only the two translocation chromosomes and no normal chromosomes 4 and 12, and half will have one normal and one translocated chromosome.
C
A plantlike organism on the planet Pandora can have three recessive genetic traits: bluish leaves, due to an allele (a) of gene A; a feathered stem, due to an allele (b) of gene B; and hollow roots due to an allele (c) of gene C. The three genes are linked and recombine.A geneticist performed a testcross with an organism that had been found to be heterozygous for the three recessive traits and she was able to identify progeny of the following phenotypic distribution (+ = wild type): The greatest distance among the three genes is between a and c. What does this mean? A. Gene c is between a and b B. Gene a is between b and c. C. Genes are in the order: a-b-c. D. Gene a is not recombining with c
B
A plantlike organism on the planet Pandora can have three recessive genetic traits: bluish leaves, due to an allele (a) of gene A; a feathered stem, due to an allele (b) of gene B; and hollow roots due to an allele (c) of gene C. The three genes are linked and recombine.A geneticist performed a testcross with an organism that had been found to be heterozygous for the three recessive traits and she was able to identify progeny of the following phenotypic distribution (+ = wild type):What is the greatest benefit of having used a testcross for this experiment? A. The homozygous recessive parents are obvious to the naked eye. B. The phenotypes of the progeny reveal the allelic content of the gamete from the heterozygous parent. C. The homozygous parents are the only ones whose crossovers make a difference. D. All of the progeny will be heterozygous.
B
A plantlike organism on the planet Pandora can have three recessive genetic traits: bluish leaves, due to an allele (a) of gene A; a feathered stem, due to an allele (b) of gene B; and hollow roots due to an allele (c) of gene C. The three genes are linked and recombine.A geneticist performed a testcross with an organism that had been found to be heterozygous for the three recessive traits and she was able to identify progeny of the following phenotypic distribution (+ = wild type):Which of the following are the phenotypes of the parents in this cross? A. 2 and 5 B. 4 and 8 C. 1 and 6 D. 3 and 7
B
A woman is found to have 47 chromosomes, including three X chromosomes. Which of the following statements describes her expected phenotype? A. a female with masculine characteristics such as facial hair B. healthy female of slightly above-average height C. a sterile female D. an apparent male who is sterile
C
All female mammals have one active X chromosome per cell instead of two. What causes this to happen? A. activation of the BARR gene on one X chromosome, which then becomes inactive B. attachment of methyl (-CH3) groups to the X chromosome that will remain active C. activation of the XIST gene on the X chromosome that will become the Barr body D. inactivation of the XIST gene on the X chromosome derived from the male parent
D
At what stage of the cell cycle is the cyclin component of MPF destroyed? a. at mid-S phase b. in early G2 c. in late G1 d. in late M
C
Between which two genes would you expect the highest frequency of recombination? A. A and E B. A and W C. A and G D. E and G
A
Cell A has half as much DNA as cells B, C, and D in a mitotically active tissue. Cell A is most likely in a. G1. b. metaphase. c. G2. d. prophase.
D
Cells from advanced malignant tumors often have very abnormal chromosomes and an abnormal number of chromosomes. What might explain the association between malignant tumors and chromosomal abnormalities? A. Cancer cells are no longer density-dependent. B. Cancer cells are no longer anchorage-dependent. C. Transformation introduces new chromosomes into cells. D. Cell cycle checkpoints are not in place to stop cells with chromosome abnormalities.
B
Cinnabar eye color is a sex-linked, recessive characteristic in fruit flies. If a female having cinnabar eyes is crossed with a wild-type male, what percentage of the F1 males will have cinnabar eyes? A. 50% B. 100% C. 0% D. 25%
C
Density-dependent inhibition is explained by which of the following processes? A. As cells become more numerous, the level of waste products increases, which slows metabolism and inhibits growth. B. As cells become more numerous, they begin to squeeze against each other, restricting their size. C. As cells become more numerous, the cell surface proteins of one cell contact the adjoining cells, and they signal each other to stop dividing. D. 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
Duchenne muscular dystrophy is a serious condition caused by a recessive allele of a gene on the human X chromosome. The patients have muscles that weaken over time because they have absent or decreased dystrophin, a muscle protein. They rarely live past their 20s. How likely is it for a woman to have this condition? A. Only if a woman is XXX could she have this condition. B. One-fourth of the daughters of an affected man would have this condition. C. Women can never have this condition. D. One-half of the daughters of an affected father and a carrier mother could have this condition.
C
During meiosis, a defect occurs in a cell that results in the failure of spindle microtubules binding at the kinetochores. Which of the following statements describes the most likely result of such a defect? A. New microtubules with more effective binding capabilities to kinetochores will be synthesized to compensate for the defect. B. Excessive cell divisions will occur resulting in cancerous tumors and an increase in the chromosome numbers known as polyploidy. C. The resulting cells will not receive the correct number of chromosomes in the gametes, a condition known as aneuploidy. D. The defect will be bypassed in order to ensure normal chromosome distribution in the new cells.
C
During which phase of mitosis do the chromatids become chromosomes? a. telophase b. metaphase c. anaphase d. prophase
C
Early observations of a cultured cell line indicated that the cells did not exhibit either density-dependent inhibition or anchorage dependence. What do these observations suggest about this cell line? a. The cells are unable to form spindle microtubules. b. The cells follow an altered series of cell cycle phases. c. The cells show characteristics of tumors. d. The cells have nonfunctional MPF.
B
Eukaryotic chromosomes are composed of which of the following macromolecules? A. DNA only B. DNA and proteins C. DNA and phospholipids D.DNA and RNA
C
Exposure of zebrafish nuclei to cytosol isolated from eggs at metaphase of mitosis resulted in phosphorylation of NEP55 and L68 proteins by cyclin-dependent kinase 2. NEP55 is a protein of the inner nuclear membrane, and L68 is a protein of the nuclear lamina. What is the most likely role of phosphorylation of these proteins in the process of mitosis? a. They are involved in chromosome condensation. b. They assist in the migration of centrosomes to opposite sides of the nucleus. c. They are involved in the disassembly of the nuclear envelope. d. They enable the attachment of the spindle microtubules to kinetochore regions of the centromere.
B
FtsZ is a bacterial cytoskeletal protein that forms a contractile ring involved in binary fission. Its function is analogous to ________. a. the mitotic spindle of eukaryotic cells b. the cleavage furrow of eukaryotic animal cells c. the microtubule-organizing center of eukaryotic cells d. the cell plate of eukaryotic plant cells
B
G1 is associated with which of the following cellular events? A. DNA replication B. normal growth and cell function C. the beginning of mitosis D. break down of the nuclear membrane
B
Generally, only female cats have the tortoiseshell phenotype for fur color. Which of the following statements explains this phenomenon A. Multiple crossovers on the Y chromosome prevent orange pigment production B. A male inherits only one allele of the X-linked gene controlling hair color. C. Only males can have Barr bodies D. The Y chromosome has a gene blocking orange coloration.
B
Genomic imprinting is generally due to the addition of methyl (-CH3) groups to C nucleotides and chemical histone changes to silence a given gene. If this depends on the sex of the parent who transmits the gene, which of the following statements must be true? A. Genes required for early development stages must not be imprinted. B Methylation must be reversible in ovarian and testicular cells C Methylation of this kind must occur more in males than in females. D. The imprints are transmitted only to gamete-producing cells.
D
German scientist Carl Correns found that the inheritance of variegated color on the leaves of certain plants was determined only by the maternal parent. What phenomenon explains this pattern of inheritance? A. genomic imprinting B. ribosome structure C. sex linkage D. inheritance of plastid genes
A
Glucose-6-phosphate dehydrogenase deficiency (G6PD) is inherited as an X-linked recessive allele in humans. A woman whose father suffered from G6PD marries a man who has the disease. What proportion of their sons would have the disease? A. 1/2 B. 1/4 C. 100% D. zero
C
How is plant cell cytokinesis different from animal cell cytokinesis? a. Plant cells divide after metaphase but before anaphase; animal cells divide after anaphase. b. The structural proteins of plant cells separate the two cells; in animal cells, a cell membrane separates the two daughter cells. c. Plant cells deposit vesicles containing cell wall building blocks on the metaphase plate; animal cells form a cleavage furrow. d. The contractile filaments found in plant cells are structures composed of carbohydrates; the cleavage furrow in animal cells is composed of contractile proteins.
B
If cell X enters meiosis, and nondisjunction of one chromosome occurs in one of its daughter cells during meiosis II, how will this affect the gametes at the completion of meiosis? A. Half of the gametes descended from cell X will be n + 1, and half will be n - 1. B. One-quarter of the gametes descended from cell X will be n + 1, one-quarter will be n - 1, and half will ben. C. Two of the four gametes descended from cell X will be haploid, and two will be diploid. D. All the gametes descended from cell X will be diploid.
C
If the cell whose nuclear material is shown in the figure continues toward completion of mitosis which of the following events would occur next? a. spindle fiber formation b. nuclear envelope breakdown c. formation of telophase nuclei d. synthesis of chromatids
A
If there are 40 centromeres in a cell at anaphase of mitosis, how many chromosomes will be found in each daughter cell following cytokinesis? a. 20 b. 40 c. 10 d. 80
D
In a Drosophila experiment a cross was made between homozygous wild-type females and yellow-bodied males. All of the resulting F1s were phenotypically wild type. However, adult flies of the F2 generation (resulting from matings of the F1s) had the characteristics shown in the figure. How is the mutant allele for yellow body inherited? A. It is dominant. B. It is incompletely dominant. C. It is codominant. D. It is recessive.
D
In a diploid cell with 5 chromosome pairs (2n = 10), how many sister chromatids will be found in a nucleus at prophase of mitosis? a. 10 b. 5 c. 40 d. 20
C
In a series of mapping experiments, the recombination frequencies for four different linked genes of Drosophila were determined as shown in the figure. Based on this information, what is the order of these genes on a chromosome map? A. cn-rb-b-vg B. rb-cn-vg-b C. b-rb-cn-vg D. vg-cn-b-rb
A
In birds, sex is determined by a ZW chromosome scheme. Males are ZZ and females are ZW. A recessive lethal allele that causes death of the embryo is sometimes present on the Z chromosome in pigeons. What would be the sex ratio in the offspring of a cross between a male that is heterozygous for the lethal allele and a normal female? A. 2:1 male to female B. 3:1 male to female C. 1:1 male to female D. 1:2 male to female
A
In cats, black fur color is determined by an X-linked allele; the other allele at this locus determines orange color. The heterozygote is tortoiseshell. What kinds of offspring would you expect from the cross of a black female and an orange male? A. tortoiseshell females; black males B. tortoiseshell females; tortoiseshell males C. black females; orange males D. orange females; black males
C
In humans, clear gender differentiation occurs not at fertilization, but after the second month of gestation. Which of the following statements describes the first event of this differentiation? A. formation of estrogens in female embryos B. formation of testosterone in male embryos C. activation of SRY in male embryos and masculinization of the gonads D.activation of SRY in females and feminization of the gonads
D
In the cells of many eukaryotic species, the nuclear envelope has to disappear to permit which of the following events in the cell cycle? a. condensation of the chromosomes b. separation of the centrosomes c. DNA synthesis d. attachment of microtubules to kinetochores
A
In the cells of some organisms, mitosis occurs without cytokinesis. This will result in a. cells with more than one nucleus. b. cell cycles lacking an S phase. c. cells that are unusually small. d. cells lacking nuclei.
C
In the figure, at which of the numbered regions would you expect to find cells at metaphase? A. II only B. IV only C. III only D. II and IV
B
In what way do kinetochore microtubules facilitate the process of splitting the centromeres? A. They use motor proteins to hydrolyze the centromere at specific arginine residues. B. They create tension by pulling toward opposite poles. C. They slide past each other like actin microfilaments. D. They phosphorylate the centromere, thereby changing its conformation.
B
Map units on a linkage map cannot be relied upon to calculate physical distances on a chromosome for which of the following reasons? A. Physical distances between genes change during the course of the cell cycle. B. The frequency of crossing over varies along the length of the chromosome. C. The gene order on the chromosomes is slightly different in every individual. D. The relationship between recombination frequency and map units is different in every individual.
D
Mitochondrial DNA is primarily involved in coding for proteins needed for protein complexes of the electron transport chain and ATP synthase. Therefore, mutations in mitochondrial genes would most affect which of the following processes? A. the storage of urine in the urinary bladder B. the movement of oxygen into erythrocytes C. DNA synthesis in cells of the immune system D. generation of ATP in muscle cells
D
Motor proteins require which of the following structures or molecules to function in the movement of chromosomes toward the poles of the mitotic spindle? a. intact centromeres b. a microtubule-organizing center c. intact cohesin d. ATP as an energy source
A
Nucleotides can be radiolabeled before they are incorporated into newly forming DNA and, therefore, can be assayed to track their incorporation. In a set of experiments, a student-faculty research team used labeled T nucleotides to study the incorporation of labeled nucleotides into a culture of lymphocytes. They found that the lymphocytes incorporated the labeled nucleotide at a significantly higher level after a pathogen was introduced into the culture. What might they conclude from this observation? A. Infection causes lymphocytes to divide more rapidly. B. Infection causes lymphocytes to increase in size. C. Infection causes lymphocyte cultures to skip some parts of the cell cycle. D. The pathogen consumed radiolabeled nucleotides.
C
Nucleotides can be radiolabeled before they are incorporated into newly synthesized DNA and, therefore, can be assayed to track their incorporation. In a set of experiments, a student-faculty research team used labeled T nucleotides and introduced these into a culture of dividing human cells at specific times. Which of the following questions might be answered by using the method described? A. When do spindle fibers attach to chromosomes? B. How many picograms of DNA are made per cell cycle? C. What is the length of the S phase of the cell cycle? D. How many cells are produced by the culture per hour?
C
Once a cell enters mitosis, the molecules that activate division must be turned off. What happens to MPF during mitosis? a. It is phosphorylated by a Cdk, which inactivates it. b. The Cdk component of MPF is degraded. c. The cyclin component of MPF is degraded. d. It is completely degraded.
A
One possible result of chromosomal breakage is for a fragment to join a nonhomologous chromosome. What is this type of chromosomal alteration called? A. translocation B. deletion C. duplication D. inversion
D
Pseudohypertrophic muscular dystrophy is a human disorder that causes gradual deterioration of the muscles. Only boys are affected, and they are always born to phenotypically normal parents. Due to the severity of the disease, the boys die in their teens. Is this disorder likely to be caused by a dominant or recessive allele? Is the inheritance of this trait sex-linked or autosomal? A. recessive, autosomal B. incomplete dominant, sex-linked C. dominant, sex-linked D. recessive, sex-linked
D
Red-green color blindness is a sex-linked recessive trait in humans. Two people with normal color vision have a color-blind son. What are the genotypes of the parents? A. XNXN and XnY B. XnXn and XnY C. XNXN and XNY D. XNXn and XNY
A
Several organisms, primarily protists, have what are called intermediate mitotic organization. What is the most probable hypothesis about these intermediate forms of cell division? a. They show some but not all of the evolutionary steps toward complete mitosis. b. They rely on totally different proteins for the processes they undergo. c. They may be more closely related to plant forms that also have unusual mitosis. d. They represent a form of cell reproduction that must have evolved completely separately from those of other organisms.
A
Sex determination in mammals is due to the SRY gene found on the Y chromosome. Which of the following situations could allow a person with an XX karyotype to develop a male phenotype? A. translocation of SRY to an X chromosome B. the presence of an extra autosomal chromosome C. the presence of one normal and one shortened (deleted) X D. the loss of the SRY gene from an autosome
A
Sex determination in mammals is due to the SRY gene found on the Y chromosome. Which of the following situations could allow a person with an XX karyotype to develop a male phenotype? A. translocation of SRY to an X chromosome B. the presence of an extra autosomal chromosome C. the presence of one normal and one shortened (deleted) X D. the loss of the SRY gene from an autosome
D
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? a. centriole duplication b. cytokinesis c. chromosome condensation d. the mitotic spindle
D
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 ________. A. G2 B. telophase C. prophase D. metaphase
A
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 ________. A. metaphase B. prophase C. telophase D. G2
B
The SRY gene is best described as ________. A. an autosomal gene that is required for the expression of genes on the X chromosome B. a gene present on the Y chromosome that triggers male development C. a gene present on the X chromosome that triggers female development D. an autosomal gene that is required for the expression of genes on the Y chromosome
B
The decline of MPF activity at the end of mitosis is due to a. the destruction of the protein kinase Cdk. b. the degradation of cyclin. c. decreased synthesis of Cdk. d. the accumulation of cyclin.
B
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? a. spindle formation b. cleavage furrow formation and cytokinesis c. spindle attachment to kinetochores d. cell elongation during anaphase
D
The pedigree in the figure shows the transmission of a trait in a particular family. Based on this pattern of transmission, the trait is most likely ________. A. sex-linked dominant B. autosomal dominant C. sex-linked recessive D.mitochondrial
E
The unlettered circle at the top of the figure shows a diploid nucleus with four chromosomes that have not yet replicated. There are two pairs of homologous chromosomes, one long and the other short. One haploid set is black, and the other is gray. The circles labeled A to E show various combinations of these chromosomes. What is the correct chromosomal condition for one daughter nucleus at telophase of mitosis? C E B D
A
Use the following information to answer the question.In a Drosophila experiment a cross was made between homozygous wild-type females and yellow-bodied males. All of the resulting F1s were phenotypically wild type. However, adult flies of the F2 generation (resulting from matings of the F1s) had the characteristics shown in the figure. How is the mutant allele for yellow body inherited? A. It is X-linked B. It is inherited by X inactivation C. It is not X-linked. D. It is Y-linked.
B
What does a recombination frequency of 50% indicate A. Abnormal meiosis has occurred. B. The two genes are likely to be located on different chromosomes. C. All of the offspring have combinations of traits that match one of the two parents. D. The genes are located on sex chromosomes.
A
What is a syndrome? A. a group of traits typically found in conjunction with a particular chromosomal aberration or gene mutation B. a characteristic facial appearance C. a trait that leads to cancer at some stage in life D. a specific characteristic that appears in conjunction with one specific aneuploidy
D
What is an adaptive advantage of recombination between linked genes? A. Recombination must occur or genes will not assort independently. B. The forces on the cell during meiosis II result in recombination. C. Recombination is required for independent assortment. D. New allele combinations are acted upon by natural selection.
A
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? a. centrosome b. centriole c. centromere d. kinetochore
B
Which of the following correctly describes a Philadelphia chromosome? A. an animal chromosome found primarily in the mid-Atlantic area of the United States B. a human chromosome 22 that has had a specific translocation C. a chromosome found only in mitochondria D. a human chromosome 9 that is found only in one type of cancer
A
Which of the following events occurs during interphase of the cell cycle? a. replication of the DNA b. spindle formation c. separation of the spindle poles d. condensation of the chromosomes
D
Which of the following individuals will inherit an X-linked allele from a man who carries it? A. half of his daughters B. all of his sons C. all of his children D. all of his daughters
A
Which of the following is an example of monosomy in human A. Turner syndrome B. Down syndrome C. trisomy X D. Klinefelter syndrome
B
Which of the following molecules is a protein maintained at steady levels throughout the cell cycle that requires cyclin to become catalytically active? A. PDGF B. Cdk C. MPF D. CYCLIN
C
Which of the following molecules is a protein synthesized at specific times during the cell cycle that associates with a kinase to form a catalytically active complex? A. PDGF B. MPF C. cyclin D. Cdk
D
Which of the following molecules is released by platelets in the vicinity of an injury? a. cyclin b. MPF c. Cdk d. PDGF
C
Which of the following molecules triggers the cell's passage past the G2 checkpoint into mitosis? a. Cdk b. PDGF c. MPF d. cyclin
C
Which of the following occurrences describes how recombination between linked genes comes about A. Nonrecombinant chromosomes break and then rejoin with one another. B. Linked genes travel together at anaphase. C. Crossovers between these genes result in chromosomal exchange. D. Independent assortment sometimes fails
B
Which of the following phrases correctly defines what one map unit is? A. 1 nanometer of distance between two genes B. a 1% frequency of recombination between two genes C. the recombination frequency between two genes assorting independently D. the physical distance between two linked genes
B
Which of the following statements correctly describes the meaning of the chromosome theory of inheritance as expressed in the early 20th century? A. Natural selection acts on certain chromosome combinations rather than on genes. B. Mendelian genes are at specific loci on the chromosome and, in turn, segregate during meiosis. C. No more than a single pair of chromosomes can be found in a healthy normal cell. D. Individuals inherit particular chromosomes attached to genes.
D
Which of the following statements is generally true of aneuploidies in newborns? A. An aneuploidy resulting in the deletion of a chromosome segment is less serious than a duplication. B. Human aneuploidy usually conveys an adaptive advantage in humans. C. A monosomy is more frequent than a trisomy. D. Monosomy X is the only viable monosomy known to occur in humans.
C
Which of the following statements regarding gene linkage is correct? A. All of the traits that Mendel studied—seed color, pod shape, flower color, and others—are due to genes linked on the same chromosome. B. Linked genes are found on different chromosomes. C. The closer two genes are on a chromosome, the lower the probability that a crossover will occur between them. D. The observed frequency of recombination of two genes that are far apart from each other has a maximum value of 100%.
D
Which of the following statements would explain a testcross involving F1 dihybrid flies in which more parental-type offspring than recombinant-type offspring are produced? A. The two genes are linked but on different chromosomes. B. Both of the characters are controlled by more than one gene C. Recombination did not occur in the cell during meiosis D. The two genes are closely linked on the same chromosome.
D
Which of the following statements would explain a testcross involving F1 dihybrid flies in which more parental-type offspring than recombinant-type offspring are produced? A. The two genes are linked but on different chromosomes. B. Both of the characters are controlled by more than one gene. C. Recombination did not occur in the cell during meiosis. D. The two genes are closely linked on the same chromosome.
D
Why are males more often affected by sex-linked traits than females? A. Male hormones such as testosterone often alter the effects of mutations on the X chromosome. B. X chromosomes in males generally have more mutations than X chromosomes in females. C. Female hormones such as estrogen often compensate for the effects of mutations on the X chromosome. D. Males are hemizygous for the X chromosome.