BIO 325 Midterm Exam 1 Questions and 100% Correct Answers 2026/27
Update - UT Austin
Your Name
UTeid
No questions will be answered during the exam.
Figuring out what the questions mean is part of the exam.
Detach the back page and use it as scratch paper.
Be sure to circle your answers.
If nothing is circled, you won’t get credit.
Reason: I will not pick the correct answer from among multiple answers.
NO CALCULATORS.
Leave numerical answers as expressions (e.g. 1/2 × 1/3 instead of 1/6 ).
Do not do the arithmetic.
It wastes your time, and you might make an error that will count against you.
You don’t have to write a long explanation, but you must show how you got your
answer. If all you have on your page is a number, there is no way for me to know if you
guessed, copied it, or what. Credit is given only for knowing how to figure out the
answer.
The entire exam contains 100 points.
Tips:
• Answer the question asked, not a different one that you prefer. (zero points for that)
• Do not supply information not asked for. That could count against you – especially if
it’s incorrect.
BIO 325 Midterm Exam 1
, 1. Recall that Mendel’s pea plants had dominant and recessive alleles of the Y gene
that control yellow (Y–) versus green (yy) peas, and dominant and recessive alleles of
the R gene that control round (R–) versus wrinkled (rr) peas. The alleles of these two
genes assort independently into gametes.
Answer the following questions about the dihybrid cross: Yy Rr × Yy Rr.
a. List all the gamete types (genotypes) that a Yy Rr dihybrid produces and their relative
frequencies. (5 points)
[1 YR : 1 yr : 1 Yr : 1 yR ] or [1/4 YR : 1/4 yr : 1/4 Yr : 1/4 yR ] or
[25% YR : 25% yr : 25% Yr : 25% yR ]
b. At what frequency would you expect green wrinkled progeny from the dihybrid cross?
Show how you know. (5 points)
1/16 (yy rr) are green wrinkled
c. Suppose 10 progeny of the dihybrid cross are in line in a pea pod. At what frequency
would you expect this pod to contain 5 green wrinkled peas and 5 yellow round peas, in
that order? (5 green wrinkled peas at the end of the pod connected to the stem,
followed by 5 yellow round peas at the other end of the pod) Show how you know. (5
points)
Frequency of green wrinkled (yy rr) is 1/16.
Frequency of yellow round (Y– R–) is 9/16.
Frequency of that specific 10-pea pod: (1/16)5 (9/16) 5
d. Recall that the binomial equation tells you the number of ways to order two different
things. If the number of Thing1 is x, and the number of Thing2 is y, recall that the
binomial equation is: (x + y)! / (x!)(y!)
At what frequency would you expect a 10-pea pod to have 5 yellow round peas and 5
green wrinkled peas, in any order? (5 points)
[10! / (5!)(5!)] [(1/16)5 (9/16)5]
[10! / (5!)(5!)] is the number of different orders of the yellow round and green wrinkled
peas in the pod.
[(1/16)5 (9/16)5] is the probability of each of [10! / (5!)(5!)] different pods.
BIO 325 Midterm Exam 1
Update - UT Austin
Your Name
UTeid
No questions will be answered during the exam.
Figuring out what the questions mean is part of the exam.
Detach the back page and use it as scratch paper.
Be sure to circle your answers.
If nothing is circled, you won’t get credit.
Reason: I will not pick the correct answer from among multiple answers.
NO CALCULATORS.
Leave numerical answers as expressions (e.g. 1/2 × 1/3 instead of 1/6 ).
Do not do the arithmetic.
It wastes your time, and you might make an error that will count against you.
You don’t have to write a long explanation, but you must show how you got your
answer. If all you have on your page is a number, there is no way for me to know if you
guessed, copied it, or what. Credit is given only for knowing how to figure out the
answer.
The entire exam contains 100 points.
Tips:
• Answer the question asked, not a different one that you prefer. (zero points for that)
• Do not supply information not asked for. That could count against you – especially if
it’s incorrect.
BIO 325 Midterm Exam 1
, 1. Recall that Mendel’s pea plants had dominant and recessive alleles of the Y gene
that control yellow (Y–) versus green (yy) peas, and dominant and recessive alleles of
the R gene that control round (R–) versus wrinkled (rr) peas. The alleles of these two
genes assort independently into gametes.
Answer the following questions about the dihybrid cross: Yy Rr × Yy Rr.
a. List all the gamete types (genotypes) that a Yy Rr dihybrid produces and their relative
frequencies. (5 points)
[1 YR : 1 yr : 1 Yr : 1 yR ] or [1/4 YR : 1/4 yr : 1/4 Yr : 1/4 yR ] or
[25% YR : 25% yr : 25% Yr : 25% yR ]
b. At what frequency would you expect green wrinkled progeny from the dihybrid cross?
Show how you know. (5 points)
1/16 (yy rr) are green wrinkled
c. Suppose 10 progeny of the dihybrid cross are in line in a pea pod. At what frequency
would you expect this pod to contain 5 green wrinkled peas and 5 yellow round peas, in
that order? (5 green wrinkled peas at the end of the pod connected to the stem,
followed by 5 yellow round peas at the other end of the pod) Show how you know. (5
points)
Frequency of green wrinkled (yy rr) is 1/16.
Frequency of yellow round (Y– R–) is 9/16.
Frequency of that specific 10-pea pod: (1/16)5 (9/16) 5
d. Recall that the binomial equation tells you the number of ways to order two different
things. If the number of Thing1 is x, and the number of Thing2 is y, recall that the
binomial equation is: (x + y)! / (x!)(y!)
At what frequency would you expect a 10-pea pod to have 5 yellow round peas and 5
green wrinkled peas, in any order? (5 points)
[10! / (5!)(5!)] [(1/16)5 (9/16)5]
[10! / (5!)(5!)] is the number of different orders of the yellow round and green wrinkled
peas in the pod.
[(1/16)5 (9/16)5] is the probability of each of [10! / (5!)(5!)] different pods.
BIO 325 Midterm Exam 1
