Download Genetics problems - University of Toronto Mississauga

1-Genetics Problems page 1 of 4
1. A sexually reproducing organism is heterozygous for two genes located on
different chromosomes, one for ear shape and one for toe length. Its
genotype is AaBb. Which of the following genotypes is most probable in a
gamete from this organism?
a. AB
b. AaBb
c. Aa
d. Bb
e. A
2. Pseudohypertrophic muscular dystrophy is a human disorder that causes
gradual deterioration of the muscles. It is seen only in boys born to
apparently normal parents and usually results in death in the early teens. It is
likely that this gene is ______ and ______.
a.
b.
c.
d.
e.
recessive; sex-linked
dominant; sex-linked
recessive; autosomal (not sex-linked)
codominant; sex-linked
incompletely dominant; autosomal (not sex-linked)
3. Assuming independent assortment for all gene pairs, what is the probability
that the following parents, AABbCc X AaBbCc will produce an AaBbCc
offspring?
a.
b.
c.
d.
e.
1/2
1/16
1/8
3/4
9/16
4. A sexually reproducing organism is heterozygous for two genes located on
different chromosomes, one for ear shape and one for toe length. Its
genotype is AaBb. Which of the following genotypes is most probable in a
gamete from this organism?
a.
b.
c.
d.
e.
AB
AaBb
Aa
Bb
A
5. Two mice are heterozygous for albinism (Aa). The dominant allele (A) codes
for normal pigmentation, and the recessive allele (a) codes for no
pigmentation. What percentage of their offspring will show albinism?
a. 25 percent
b. 50 percent
c. 75 percent
d. 100 percent
BIO152H 2006 University of Toronto at Mississauga
1-Genetics Problems page 2 of 4
6. Which of the following is due to the principle of segregation?
a. Each gamete has an equal chance of getting either allele for a gene.
b. Each gamete formed in an organism will have one copy of each gene.
c. Half of the gametes produced by an individual that is AaBb will be AB.
d. Each gamete formed in an organism has two copies of each gene.
7. If the first five seeds (offspring) grown from a cross between two
heterozygous parent peas with the genotype Rr are all round, what is the
probability that the next offspring will be wrinkled?
a. 0%
b. 100%
c. 25%
d. Cannot determine from the information given
8. In a cross between peas heterozygous for two traits , the probability of the
offspring exhibiting both recessive traits is 1/16. What is the probability of
exhibiting recessive traits when both parents are heterozygous for three
traits?
a. 1/4
b. 1/16
c. 1/64
d. 27/64
9. If an organism is heterozygous for two traits that are linked, how many
genotypes are possible in the gametes produced from a single germ-line cell?
Assume that no crossing over occurs.
a. 1
b. 2
c. 4
d. 8
10. What is the fundamental difference between mitosis and meiosis?
a. Mitosis involves two cell divisions; meiosis has only one.
b. The number of chromosomes doubles in meiosis; the number stays
the same in mitosis.
c. The amount of DNA is reduced by half in meiosis, but remains the
same in mitosis
d. Meiosis occurs in prokaryotes; mitosis occurs in eukaryotes.
11. A species has six pairs of chromosomes. How many molecules of DNA do
the nuclei have during G2 phase?
a. 6
b. 12
c. 24
d. 48
BIO152H 2006 University of Toronto at Mississauga
1-Genetics Problems page 3 of 4
12. Which of the following pairs of genes would demonstrate the highest
incidence of crossing over?
a.
b.
c.
d.
Gene a and gene b
Gene c and gene d
Gene d and gene e
Gene e and gene f
13. Although the partitioning of chromosomes is visible during mitosis and
meiosis with the aid of the light microscope, DNA replication is not. Why?
a. Chromosomes only form during mitosis or meiosis.
b. Chromosomes are only visible after DNA has been duplicated.
c. Chromosomes are too extended during S phase to be seen by light
microscopy.
14. Which of the following occurs during meiosis II, but not during meiosis I?
a. Crossing over between homologous chromosomes.
b. Separation of homologous chromosomes.
c. Separation of sister chromatids.
d. Chromosome migration to the poles.
15. Robert’s father has brown eyes & brown hair; his mother has blue eyes &
blonde hair. Explain how Robert has a daughter with brown eyes and blonde
hair (genetic tests have shown Robert contributed these traits to his daughter
and assume these traits are linked)
a. Independent assortment
b. Crossing over of Robert’s mother’s chromosomes
c. Crossing over of Robert’s father’s chromosomes
d. Crossing over of Robert’s genes.
16. If an organism is heterozygous for two traits that are linked, how many
different genotypes are possible in the gametes? Assume no crossing over
occurs.
a. 1
b. 2
c. 4
d. 8
BIO152H 2006 University of Toronto at Mississauga
1-Genetics Problems page 4 of 4
17. If an organism is heterozygous for two traits that are linked, how many
different genotypes are possible in the gametes produced from a single germ
line if even a single crossing over event occurs?
a. 1
b. 2
c. 4
d. 8
18. Diagram meiotic crossing over between two genes on the same
chromosome. Parental cell entering into meiosis is aB/Ab What are all of the
possible GENOTYPES of the gametes?
19. A sexually reproducing organism is heterozygous for two genes located on
different chromosomes, one for ear shape and one for toe length. Its
genotype is AaBb. Which of the following genotypes is most probable in a
gamete from this organism?
a. AB
b. AaBb
c. Aa
d. Bb
e. A
20. A man and woman are both of normal pigmentation, but both have one
parent who is albino (without melanin pigmentation). Albinism is an
autosomal (not sex-linked) recessive trait. What is the probability that their
first child will be an albino?
A.
0%
B.
1/8
C.
1/2
D.
1/4
E.
100%
BIO152H 2006 University of Toronto at Mississauga