Among the F2 offspring, what is the probability of plants with white axial flowers?
A) 9/16
B) 1/16
C) 3/16
D) 1/8
E) 1/4

3/16

Labrador retrievers are black, brown, or yellow. In a cross of a black female with a brown male,
results can be either all black puppies, 1/2 black to 1/2 brown puppies, or 3/4 black to 1/4 yellow
puppies.

These results indicate which of the following?
A) Brown is dominant to black.
B) Black is dominant to brown and to yellow.
C) Yellow is dominant to black.
D) There is incomplete dominance.
E) Epistasis is involved.

Epistasis is involved.

How many genes must be responsible for these coat colors in Labrador retrievers?
A) 1
B) 2
C) 3
D) 4
E) 5

2

In one type cross of black × black, the results were as follows:
9/16 black
4/16 yellow
3/16 brown
The genotype eebb must result in which of the following?
A) black
B) brown
C) yellow
D) a lethal result
E) white

yellow

Radish flowers may be red, purple, or white. A cross between a red-flowered plant and a white-
flowered plant yields all-purple offspring. The part of the radish we eat may be oval or long, with
long being the dominant trait.

If true-breeding red long radishes are crossed with true-breeding white oval radishes, the F1
will be expected to be which of the following?
A) red and long
B) red and oval
C) white and long
D) purple and long
E) purple and oval

purple and long

In the F2 generation of the above cross, which of the following phenotypic ratios would be
expected?
A) 9:3:3:1
B) 9:4:3
C) 1:1:1:1
D) 1:1:1:1:1:1
E) 6:3:3:2:1:1

6:3:3:2:1:1

8) The flower color trait in radishes is an example of which of the following?
A) a multiple allelic system
B) sex linkage
C) codominance
D) incomplete dominance
E) epistasis

incomplete dominance

Drosophila (fruit flies) usually have long wings (+), but mutations in two different genes can
result in bent wings (bt) or vestigial wings (vg).

If a homozygous bent wing fly is mated with a homozygous vestigial wing fly, which of the
following offspring would you expect?
A) all +bt +vg heterozygotes
B) 1/2 bent and 1/2 vestigial flies
C) all homozygous + flies
D) 3/4 bent to 1/4 vestigial ratio
E) 1/2 bent and vestigial to 1/2 normal

all +bt +vg heterozygotes

If flies that are heterozygous for both the bent wing gene and the vestigial wing gene are
mated, what is the probability of offspring with bent wings only?
A) 1/8
B) 3/8
C) 1/4
D) 9/16
E) 3/16

3/16

Tallness (T) in snapdragons is dominant to dwarfness (t), and red (R) flower color is dominant to
white (r). The heterozygous condition results in pink (Rr) flower color.

A dwarf, red snapdragon is crossed with a plant homozygous for tallness and white flowers.
What are the genotype and phenotype of the F1 individuals?
A) ttRr–dwarf and pink
B) ttrr–dwarf and white
C) TtRr–tall and red
D) TtRr–tall and pink
E) TTRR–tall and red

TtRr–tall and pink