3.04 Quiz
Answer Key
Question 1 (Worth 2 points)
In a monohybrid cross, if the gene for tall (T) plants was incompletely dominant over the gene for short
(t) plants, what would be the predicted result of crossing an intermediate (Tt) plant with a tall (TT)
plant? (Hint: You may want to complete a Punnett square)
50 percent tall, 25 percent intermediate, 25 percent short
25 percent tall, 50 percent intermediate, 25 percent short
50 percent tall, 50 percent intermediate
100 percent intermediate
Points earned on this question: 0
Question 2 (Worth 2 points)
If a baby boy inherits a recessive allele from his mother, in which of the following circumstances would
he most likely exhibit that recessive trait?
The allele is X-linked.
His mother’s father also exhibited the trait.
The allele skips a generation.
He inherited the dominant trait from his father.
Points earned on this question: 2
Question 3 (Worth 2 points)
The allele for a widow’s peak has complete dominance over the allele for a straight hairline (w). What is
the probability of two parents heterozygous for a widow’s peak (Ww) having an offspring with a widow’s
peak?
75 percent
50 percent
0 percent
25 percent
Points earned on this question: 2
Question 4 (Worth 2 points)
Which of the following genotypes is homozygous dominant?
tt
Ff
XY
SS
Points earned on this question: 2
Question 5 (Worth 2 points)
In fruit flies, the gene for red eyes (R) is dominant and the gene for sepia eyes (r) is recessive. If a redeyed homozygous fly (RR) and a red-eyed heterozygous fly (Rr) mate together, what are the possible
genotypes of their offspring? (Hint: You many want to complete a Punnett square.)
RR and rr
Rr only
Rr and RR
RR, Rr, and rr
Points earned on this question: 2
Question 6 (Worth 2 points)
If a pea plant has a genotype SSTt, what are the possible genetic combinations that could be present in a
single grain of pollen produced by the plant?
SS, Tt, ST
ST, St, st
SS, Tt, ST, St
ST, St
Points earned on this question: 2
Question 7 (Worth 2 points)
What are the genotypes of the parents in the monohybrid cross below if the following offspring
genotypes are predicted?
?
? TT
?
Tt
? Tt
tt
Tt and Tt
TT and tt
Tt and TT
Tt and tt
Points earned on this question: 2
Question 8 (Worth 2 points)
A mouse’s tail gets cut off. If the mouse has babies later, how will this affect the length of the tails of its
offspring?
It depends on the length of the mate’s tail.
It will not affect the length of the tails of any of the offspring.
It will affect the length of the tails of all the offspring.
It will affect the length of the tails of some of the offspring.
Points earned on this question: 2
Question 9 (Worth 2 points)
This pedigree chart tracks the inheritance of a recessive trait that is not sex-linked. Based on the
information in the chart, which of the following statements is true?
Individual #8 must be heterozygous for the trait.
Individual #10 must be heterozygous for the trait.
Individual #13 must be homozygous dominant.
Individual #3 must be homozygous dominant.
Points earned on this question: 2
Question 10 (Worth 5 points)
In one type of plant, orange petals (O) are dominant over yellow petals (o) and tall stems (T) are
dominant over short stems (t). Complete a dihybrid cross for parents with the genotypes: OOTt × OoTt
and answer the following in complete sentences.
1. Describe how you would set up a Punnett square for this cross.
2. List the likelihood of each possible offspring genotype.
3. List the likelihood of each possible offspring phenotype.
Essay Submission
1. The Punnet Square would be a
2. Each possible offspring genotype is OOTT, OOTt, OoTt, OOtt, OoTT, Oott.
3. There is a 75% chance for Orange Petals, and 18% chance for Yellow Petals. As well as a 50% chance
for short and tall stems.
Points earned on this question: 5