BIO 325 Genetics Problem Set 1 Questions and Answers 2026/27 Latest - UT Austin
1. For an organism that is AaBb, A. show (draw) how their chromosomes will look at Meiosis 1 B. Show
what gametes they will make and in what proportions.
A B a B
A B a B
a b
b
OR A
b
b
a A
B. ¼ AB, ¼ Ab, aB ¼ , ¼ ab
2. Regarding Humans
A. Humans have how many chromosomes? 46
B. Humans have how many autosomes? _44
C. How many autosomes are present in a sperm cell? _22
D. How many chromosomes are present in a sperm cell? 23
E. What is the diploid number of chromosomes? 46
F. What is the haploid number of chromosomes? 23
3. Consider three independently assorting gene pairs Aa, Bb, and Cc.' What is the probability (give a
fraction) of obtaining each of the following genotypes from parents that are AaBbCC and AaBBCc?'
AABbCC 1/4 x ½ x 1/2
aaBBCc 1/4 x ½ x 1/2
aabbCC 0
BIO 325 Genetics Problem Set 1
, 4. You have grown up 20 plants from 20 yellow seeds. Assume that Y_ is yellow and yy is green. You do
not know if those yellow seeds were homozygous or heterozygous. You want to identify the homozygous
plants. What can you do to figure this out?
You do a test cross where you cross the plants grown from yellow seeds with true-breeding plants that
have green seeds
What will be the result if the original plant was homozygous? Yellow seeds
What will be the result if the original plant was heterozygous? Yellow and Green seeds
5. If you cross heterozygotes (Yy x Yy) where Y_ are yellow seeds and yy are green, what fraction of the
offspring will be will have yellow seeds, what fraction will have green seeds? If you cross heterozygotes
(Rr x Rr) where R are round seeds and rr are wrinkled , what fraction of the offspring will have round
seeds, what fraction will have wrinkled seeds. If you now set up a Punnet square with a cross between
these two using the numbers you obtained, what will be the results?
Yellow 3/4 Green 1/4
Round 3/4 9/16 yellow round 3/16 Round green
Wrinkled 1/4 3/16 yellow wrinkled 1/16 green wrinkled
6. In some genetically engineered corn plants the dominant gene (BT) produces a protein that is
lethal to certain flying insect pests that eat the corn plants. It was also found that the pollen could
cause death in some flying insects. If the corn plant is heterozygous for BT, what proportion of
the pollen would carry the dominant gene?
A. all pollen
B. 1/2
C. 1/3
D. 1/4
E. 1/8
7. In a monohybrid cross AA × aa, what proportion of homozygotes is expected among the F2
offspring?
A. 1/4
B. 1/2
C. 3/4
D. All are homozygotes.
E. None are homozygotes.
BIO 325 Genetics Problem Set 1
1. For an organism that is AaBb, A. show (draw) how their chromosomes will look at Meiosis 1 B. Show
what gametes they will make and in what proportions.
A B a B
A B a B
a b
b
OR A
b
b
a A
B. ¼ AB, ¼ Ab, aB ¼ , ¼ ab
2. Regarding Humans
A. Humans have how many chromosomes? 46
B. Humans have how many autosomes? _44
C. How many autosomes are present in a sperm cell? _22
D. How many chromosomes are present in a sperm cell? 23
E. What is the diploid number of chromosomes? 46
F. What is the haploid number of chromosomes? 23
3. Consider three independently assorting gene pairs Aa, Bb, and Cc.' What is the probability (give a
fraction) of obtaining each of the following genotypes from parents that are AaBbCC and AaBBCc?'
AABbCC 1/4 x ½ x 1/2
aaBBCc 1/4 x ½ x 1/2
aabbCC 0
BIO 325 Genetics Problem Set 1
, 4. You have grown up 20 plants from 20 yellow seeds. Assume that Y_ is yellow and yy is green. You do
not know if those yellow seeds were homozygous or heterozygous. You want to identify the homozygous
plants. What can you do to figure this out?
You do a test cross where you cross the plants grown from yellow seeds with true-breeding plants that
have green seeds
What will be the result if the original plant was homozygous? Yellow seeds
What will be the result if the original plant was heterozygous? Yellow and Green seeds
5. If you cross heterozygotes (Yy x Yy) where Y_ are yellow seeds and yy are green, what fraction of the
offspring will be will have yellow seeds, what fraction will have green seeds? If you cross heterozygotes
(Rr x Rr) where R are round seeds and rr are wrinkled , what fraction of the offspring will have round
seeds, what fraction will have wrinkled seeds. If you now set up a Punnet square with a cross between
these two using the numbers you obtained, what will be the results?
Yellow 3/4 Green 1/4
Round 3/4 9/16 yellow round 3/16 Round green
Wrinkled 1/4 3/16 yellow wrinkled 1/16 green wrinkled
6. In some genetically engineered corn plants the dominant gene (BT) produces a protein that is
lethal to certain flying insect pests that eat the corn plants. It was also found that the pollen could
cause death in some flying insects. If the corn plant is heterozygous for BT, what proportion of
the pollen would carry the dominant gene?
A. all pollen
B. 1/2
C. 1/3
D. 1/4
E. 1/8
7. In a monohybrid cross AA × aa, what proportion of homozygotes is expected among the F2
offspring?
A. 1/4
B. 1/2
C. 3/4
D. All are homozygotes.
E. None are homozygotes.
BIO 325 Genetics Problem Set 1
