Review questions

Question 1

Which phenomenon explains differences in the inheritance patterns of the appearance of a chin beard between males and females of certain species of goats, even when their genotypes are the same?
A) sex-limited trait
B) sex-influenced trait
C) incomplete penetrance
D) variable expressivity
E) lethal allele

Answer 1

B) sex-influenced trait

Question 2

In certain goat breeds, appearance of a chin beard is a sex-influenced trait. Recall that bearding is inherited as an autosomal trait determined by
two alleles, B1 and B2, and females must be homozygous for the bearded allele, B2, to have a beard. What genotypes must a bearded billy goat
(male) and a beardless female goat have if they have a bearded female offspring?
A) The bearded billy goat must be heterozygous for the bearded allele, while the beardless female must be homozygous for the bearded allele.
B) Both the bearded billy goat and beardless female must be heterozygous for the bearded allele.
C) The bearded billy goat could be heterozygous or homozygous for the bearded allele, while the beardless female must be heterozygous for the
bearded allele.
D) Both the bearded billy goat and beardless female must be homozygous for the bearded allele.
E) The bearded billy goat could be heterozygous or homozygous for the bearded allele, while the beardless female must be homozygous for the bearded allele.

Answer 2

C) The bearded billy goat could be heterozygous or homozygous for the bearded allele, while the beardless female must be heterozygous for the
bearded allele.

Question 3

The color of sunflower pollen can be orange, yellow,
or white-cream. Crosses reveal that true-breeding
orange is dominant to both yellow and white-cream.
However, a cross between true-breeding white-
cream and yellow plants produced F1 plants with
orange pollen. The F2 populations of this cross
resulted in a ratio of nine orange:three yellow:four
white-cream. What type of inheritance do these
results suggest?
A. Dominant epistasis
B. Recessive epistasis
C. Dependent assortment
D. Incomplete dominance
E. Codominance

Answer 3

B. Recessive epistasis

Question 4

The A and B genes are 20 map units
apart. What proportion of the gametes
produced by an individual with
genotype Ab/aB will be AB?
a) 10%
b) 20%
c) 25%
d) 40%

Answer 4

a) 10%

Question 5

True-breeding parents (AAbb and aaBB) are
crossed. A test cross of the F1 produces the
progeny ratios below. How far apart are the
A and B genes?
a) 12 map units
b) 24 map units
c) 38 map units
d) 76 map units
Progeny ratios: 0.11 AB, 0.13 ab, 0.38 Ab, 0.38 aB

Answer 5

b) 24 map units

Question 6

Test-crossing a triple heterozygote (AaBbDd)
produces the phenotype ratios in the table
below. Determine the gene order by
inspection.
a) A - B - D
b) B - A - D
c) A - D - B

Answer 6

c) A - D - B

Question 7

Why are chromosomes more easily visible under a microscope during Metaphase as compared to G2 phase?
*A) They become stained by natural pigments in the cell.
*B) There is twice as much DNA during Metaphase than during G2 phase.
*C) Chromosomes are contained in the nucleus during G2 but not during metaphase.
*D) Proteins that bind chromosomes during Metaphase are highly visible.
*E) They are highly condensed in Metaphase

Answer 7

E) They are highly condensed in Metaphase.

Question 8

Meiosis allows _____.
A. the generation of genetic variation among offspring
B. the generation of new combinations of alleles on the same chromosome
C. the transmission of an equivalent amount of genetic information from generation to generation
D. the genetic contribution of two individual parents to each offspring
E. all of the above

Answer 8

E. all of the above

Question 9

This is a picture of a cell from an organism
whose somatic cells are 2n. What stage of
mitosis or meiosis is this cell in?
A. Metaphase of mitosis
B. Metaphase I of meiosis I
C. Metaphase II of meiosis II
D. Could be either metaphase of mitosis
or metaphase II of meiosis II
E. Impossible to tell

Answer 9

B. Metaphase I of meiosis I

Question 10

This picture depicts a cell that started out as 2n = 4. What stage of mitosis or meiosis is it in?
A. Prophase
B. Metaphase
C. Metaphase I
D. Metaphase II
E. Could be either metaphase or metaphase II

Answer 10

B. Metaphase

Question 11

A dihybrid has the genotype AaBb. After a normal mitotic division into two daughters cells, one daughter cell will have the genotype ________ and the other will have the genotype
________.
*A) Aa; Bb
*B) AaBb; AaBb
*C) AB; ab
*D) Ab; aB
*E) AABB; aabb

Answer 11

*B) AaBb; AaBb

Question 12

During oogenesis in animals,
A. Only two daughter cells (one from each division in meiosis) develop into ova (egg cells).
B. Only one cell gets chromosomes, the rest are polar bodies.
C. All cells get an equal share of the cytoplasm in meiosis I, but unequal share in meiosis II.
D. There can be very long time gaps (years) between one stage and the next.
E. Is very similar to spermatogenesis.

Answer 12

D. There can be very long time gaps (years) between one stage and the next.

Question 13

A single chromosome at metaphase contains how many DNA molecules?
*A) one
*B) two
*C) four
*D) more than four
*E) impossible to determine

Answer 13

B) two

Question 14

A eukaryotic cell is diploid and contains 6 chromosomes during G1 phase. If the cell undergoes mitosis, how many daughter cells would be produced, and how many chromosomes would each one contain?
* A) 2 daughter cells with 3 chromosomes each
* B) 2 daughter cells with 6 chromosomes each
* C) 2 daughter cells with 12 chromosomes each
* D) 4 daughter cells with 6 chromosomes each
* E) 4 daughter cells with 12 chromosomes each

Answer 14

• B) 2 daughter cells with 6 chromosomes each

Question 15

Modern genetics consists of three major branches. Which of these branches, also known as “transmission genetics,” involves the study of the transmission of traits and characteristics in successive generations?
*A) evolutionary
*B) Mendelian
*C) molecular
*D) population
*E) reproductive

Answer 15

*B) Mendelian

Question 16

Mendel’s third postulate is “During the formation of gametes, the paired unit factors separate, or segregate, randomly so that each gamete receives one or the other with equal likelihood.” When does this segregation occur?
A. In G1
B. In mitotic anaphase
C. In meiotic anaphase I
D. In meiotic anaphase II
E. In both meiotic anaphase I and anaphase II

Answer 16

C. In meiotic anaphase I

Question 17

Genetic experiments have revealed the relationship between the observable traits of an organism, or ________, and the genetic constitution of an organism, or ________

Answer 17

phenotype; genotype

Question 18

Genetic crosses in which F1 plants heterozygous for a given allele are crossed to generate a 3:1 phenotypic ratio in the F2 generation are known as ________.
*A) replicate crosses
*B) reciprocal crosses
*C) test crosses
*D) monohybrid crosses
*E) dihybrid crosses

Answer 18

D) monohybrid crosses

Question 19

Of the following characteristics, which is least important for a species to possess in order for it to serve as a model organism?
A. Availability of mutant strains
B. Easy growth and maintenance
C. Close evolutionary relationship to humans
D. Short reproductive cycle
E. Produce many offspring

Answer 19

C. Close evolutionary relationship to humans

Question 20

n a cross between two individuals BbGG × Bbgg, what ratio of phenotypes would be expected in the offspring if the two genes show independent assortment?
A. 1:2:1
B. 9:3:3:1
C. 1:1
D. 3:1
E. 2:1

Answer 20

D. 3:1

Question 21

You count 1000 F2 seeds from a monohybrid cross. How many seeds do you expect to display the dominant phenotype?
*A) 1000
*B) 750
*C) 500
*D) 250
*E) 0

Answer 21

*B) 750

Question 22

*Two pure-breeding mutant plants produce white flowers. When they are crossed, all of the progeny have wild-type purple flowers. What does this genetic complementation tell you?
*A) The genes are part of two distinct biosynthetic pathways.
*B) The two lines exhibit different mutations in the same gene.
*C) More than one gene is involved in determining the phenotype.
*D) The allele is pleiotropic.
*E) The allele exhibits incomplete dominance.

Answer 22

C) More than one gene is involved in determining the phenotype

Question 23

What type of allele is often detected as a distortion in segregation ratios, where one class of expected progeny is missing?
*A) dominant negative allele
*B) temperature-sensitive allele
*C) lethal allele
*D) partially dominant allele
*E) incompletely penetrant allele

Answer 23

C) lethal allele

Question 24

What is the name given to a chromosome with a centrally located centromere and Chromosome arms of essentially equal length?
a) metacentric
b) submetacentric
c) acrocentric
d) telocentric

Answer 24

a) metacentric

Question 25

The beads-on-a-string form of chromatin comprised of nucleosomes plus linker DNA is known as:
a) the 2-nm helix.
b) the 10-nm fiber.
c) the 30-nm fiber
(solenoid).
d) the 300-nm looped
chromatin.

Answer 25

b) the 10-nm fiber.

Question 26

An acentric chromosome fragment is produced by recombination between a rearranged and normal homolog in which of the following?
a) partial chromosome
duplication
b) paracentric inversion
c) pericentric inversion
d) reciprocal translocation

Answer 26

b) paracentric inversion

Question 27

Nondisjunction in meiosis 1 results in ______
A. 2 normal gametes and 2 abnormal gametes
B. 2 gametes that are n+1 and 2 gametes that are n-1
C. 4 normal gametes
D. normal chromosome complements in meiosis 2 cells, but
abnormal after completion of meiosis
E. nondisjunction in meiosis 2 also

Answer 27

B. 2 gametes that are n+1 and 2 gametes that are n-1

Question 28

human individual with 45 chromosomes has a _____.
A. monosomy
B. trisomy
C. monoploidy
D. diploidy
E. triploidy

Answer 28

A. monosomy

Question 29

The genes ABC occur in that order in fruit flies. A is 10 map units from B, and B is 20 map units
from C. What is the expected frequency of
double crossovers?
A. .02 %
B. 2%
C. 10%
D. 20%
E. 30%

Answer 29

B. 2%

Question 30

Two genes that are 60 map units apart are expected to show ______.
A. independent assortment
B. 25 percent recombination
C. 30 percent recombination
D. 50 percent recombination
E. 60 percent recombination

Answer 30

A. independent assortment

Question 31

The genes ABC occur in that order in fruit flies. A is 10 map units from B, and B is 20map units from C. How far is A from C?
A. 0.2 map units
B. 10 map units
C. 20 map units
D. 30 map units
E. 40 map units

Answer 31

D. 30 map units

Question 32

Independent assortment occurs _____.
A. between two different alleles of the same gene (e.g., A and a)
B. between alleles of the same gene, but only when they are identical (e.g., only AA or aa)
C. between the alleles of two different genes, but only when they are both heterozygous (e.g., AaBb × AaBb)
D. between two genes linked together close on the chromosome
E. between any two unlinked genes

Answer 32

E. between any two unlinked genes