Chapter 15 Multiple Choice Questions

Question 1

1) Chromosomes and genes share all of the following characteristics except that
A) they are both present in pairs in all diploid cells.
B) they both undergo segregation during meiosis.
C) their copy numbers in the cell decrease after meiosis, and increase during fertilization.
D) they are both copied during the S phase of the cell cycle.
E) they both pair up with their homologues during prophase of mitosis.

Answer 1

E. they both pair up with their homologues during prophase of mitosis.

Question 2

2) The improvement of microscopy techniques in the late 1800s set the stage for the emergence of modern genetics because
A) it revealed new and unanticipated features of Mendel’s pea plant varieties.
B) it allowed biologists to study meiosis and mitosis, revealing the parallels between the behaviors of genes and chromosomes.
C) it allowed scientists to see the DNA present within chromosomes.
D) it led to the discovery of mitochondria.
E) All of the above are true.

Answer 2

B) it allowed biologists to study meiosis and mitosis, revealing the parallels between the behaviors of genes and chromosomes.

Question 3

3) 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 involved gene was on the X chromosome.
B) The involved gene was on the Y chromosome.
C) The involved gene was on an autosome.
D) Other male-specific factors influence eye color in flies.
E) Other female-specific factors influence eye color in flies.

Answer 3

A) The involved gene was on the X chromosome.

Question 4

4) Which of the following statements is (are) true?
A) The closer two genes are on a chromosome, the higher the probability that a crossover will occur between them.
B) The observed frequency of recombination of two genes that are far apart from each other has a maximum value of 50%.
C) Two of the traits that Mendel studied-seed color and flower color-are linked on the same chromosome.
D) Only B and C are correct.
E) A, B, and C are correct.

Answer 4

D) Only B and C are correct.

Question 5

5) How would one 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.
B) The two genes are unlinked.
C) Recombination did not occur in the cell during meiosis.
D) The testcross was improperly performed.
E) Both of the characters are controlled by more than one gene.

Answer 5

A) The two genes are linked.

Question 6

6)  New combinations of linked genes are due to which of the following? 
A) nondisjunction 
B) crossing over 	
C) independent assortment 
D) mixing of sperm and egg 
E) both A and C

Answer 6

B) crossing over

Question 7

7) What does a frequency of recombination of 50% indicate?
A) The two genes likely are located on different chromosomes.
B) All of the offspring have combinations of traits that match one of the two parents.
C) The genes are located on sex chromosomes.
D) Abnormal meiosis has occurred.
E) Independent assortment is hindered.

Answer 7

A) The two genes likely are located on different chromosomes.

Question 8

12) A 0.1% frequency of recombination is observed
A) only in sex chromosomes.
B) only on genetic maps of viral chromosomes.
C) on unlinked chromosomes.
D) in any two genes on different chromosomes.
E) in genes located very close to one another on the same chromosome.

Answer 8

E) in genes located very close to one another on the same chromosome.

Question 9

14) The reason that linked genes are inherited together is that
A) they are located on the same chromosome.
B) the number of genes in a cell is greater than the number of chromosomes.
C) chromosomes are unbreakable.
D) alleles are paired.
E) genes align that way during metaphase I.

Answer 9

A) they are located on the same chromosome.

Question 10

15) What is the mechanism for the production of genetic recombinants?
A) X inactivation
B) methylation of cytosine
C) crossing over and independent assortment
D) nondisjunction
E) deletions and duplications during meiosis

Answer 10

C) crossing over and independent assortment

Question 11

16) There is good evidence for linkage when
A) two genes occur together in the same gamete.
B) a gene is associated with a specific phenotype.
C) two genes work together to control a specific characteristic.
D) genes do not segregate independently during meiosis.
E) two characteristics are caused by a single gene.

Answer 11

D) genes do not segregate independently during meiosis

Question 12

21) Which of the following is true regarding linkage maps? They
A) always have a total of 100 map units.
B) can be used to pinpoint the precise physical position of a gene on a chromosome.
C) are a genetic map based on recombination frequencies.
D) require preparation of karyotypes.
E) reflect the frequency of crossing over between X and Y chromosomes

Answer 12

C) are a genetic map based on recombination frequencies.

Question 13

22) The frequency of crossing over between any two linked genes is
A) higher if they are recessive.
B) different between males and females.
C) determined by their relative dominance.
D) the same as if they were not linked.
E) proportional to the distance between them.

Answer 13

E) proportional to the distance between them.

Question 14

23) Sturtevant provided genetic evidence for the existence of four pairs of chromosomes in Drosophila by showing that
A) there are four major functional classes of genes in Drosophila.
B) Drosophila genes cluster into four distinct groups of linked genes.
C) the overall number of genes in Drosophila is a multiple of four.
D) the entire Drosophila genome has approximately 400 map units.
E) Drosophila genes have, on average, four different alleles.

Answer 14

B) Drosophila genes cluster into four distinct groups of linked genes.

Question 15

24) Map units on a linkage map cannot be relied upon to calculate physical distances on a chromosome because
A) the frequency of crossing over varies along the length of the chromosome.
B) the relationship between recombination frequency and map units is different in every individual.
C) physical distances between genes change during the course of the cell cycle.
D) the gene order on the chromosomes is slightly different in every individual.
E) all of the above

Answer 15

A) the frequency of crossing over varies along the length of the chromosome.

Question 16

25)  A map of a chromosome that includes the positions of genes relative to visible chromosomal features, such as stained bands, is called a  
A) linkage map. 
B) physical map. 
C) recombination map. 
D) cytogenetic map.
E) banded map.

Answer 16

D) cytogenetic map.

Question 17

26) Males are more often affected by sex-linked traits than females because
A) males are hemizygous for the X chromosome.
B) male hormones such as testosterone often exacerbate the effects of mutations on the X chromosome.
C) female hormones such as estrogen often compensate for the effects of mutations on the X.
D) X chromosomes in males generally have more mutations than X chromosomes in females.
E) mutations on the Y chromosome often exacerbate the effects of X-linked mutations.

Answer 17

A) males are hemizygous for the X chromosome.

Question 18

31) SRY is
A) a gene present on the Y chromosome that triggers male development.
B) a gene present on the X chromosome that triggers female development.
C) an autosomal gene that is required for the expression of genes on the Y chromosome.
D) an autosomal gene that is required for the expression of genes on the X chromosome.
E) required for development, and males or females lacking the gene do not survive past early childhood

Answer 18

A) a gene present on the Y chromosome that triggers male development.

Question 19

32) In cats, black fur color is caused by an X-linked allele; the other allele at this locus causes 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 female; tortoiseshell male
B) black female; orange male
C) orange female; orange male
D) tortoiseshell female; black male
E) orange female; black male

Answer 19

D) tortoiseshell female; black male

Question 20

33)  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) XcXc and XcY 
B) XcXc and XCY 
C) XCXC and XcY  
D) XCXC and XCY 
E) XCXc and XCY

Answer 20

E) XCXc and XCY