plant heterozygous for inflated pods (Ii) is crossed with a plant homozygous
for constricted pods (ii). Draw a
Punnett square for this cross. Assume
pollen comes from the ii plant.
A cross of Ii x ii would yield offspring with a genotypic ratio of : and a phenotypic ratio of inflated : constricted
Pea plants heterozygous for flower position and
stem length (AaTt) are allowed to self-pollinate, and 400 of the resulting
seeds are planted. Draw a Punnett square
for this cross. How many offspring would
be predicted to have terminal flowers and be dwarf?
According to the law of , plants are predicted to be aatt, or recessive for both characters. The actual result is likely to differ slightly from this value.
List the different gametes that could be made by
a pea plant heterozygous for seed color, seed shape, and pod shape
(YyRrIi). How large a Punnett square
would you need to predict the offspring of a self-pollination of this
The plant could make eight different gametes ( , , , , , , , ) To fit all the possible gametes in a self-pollination, a Punnet square would need rows and columns. It would have spaces for the possible unions of gametes in the offspring.
For any gene with a dominant allele C and
recessive allele c, what proportions of the offspring from a CC x Cc cross are
expected to be homozygous dominant, homozygous recessive, and heterozygous?
homozygous dominant (CC), homozygous recessive (cc), and heterozygous (Cc)
An organism with the genotype BbDD is mated to
one with the genotype BBDd. Assuming independent
assortment of these two genes, write the genotypes of all possible offspring
from this cross and use the rules of probability to calculate the chance of
each genotype occurring.
BBDD; BbDD; BBDd; BbDd
Three characters (flower color, seed color, and
pod shape) are considered in a cross between two pea plants (PpYyIi x
ppYyii). What fraction of the offspring
would be predicted to be homozygous recessive for at least two of the three
The genotypes and frequencies to fulfill this condition are
Incomplete dominance and epistasis are both
terms that define genetic relationships.
What is the most basic distinction between these terms?
describes the relationship between two alleles of a , whereas relates o the genetic relationship between two
If a man with type AB blood marries a woman with
type O blood, what blood types would you expect in their children?
of the children would be expected to have to have type A blood and type B blood.
A rooster with gray feathers is mated with a hen
of the same phenotype. Among their
offspring, 15 chicks are gray, 6 are black, and 8 are white. What is the simplest explanation for the
inheritance of these colors in chickens?
What phenotypes would you expect in the offspring of a cross between a
gray rooster and a black hen?
The black and white alleles ar expressing , with gray in color. A cross between a gray rooster and a black hen should yield gray and blackoffspring.
Beth and Tom each have a sibling with cystic
fibrosis, but neither Beth nor Tom nor any of their parents have the
disease. Calculate the probability that
if this couple has a child, the child will have cystic fibrosis. What would be the probability if a test
revealed that Tom is a carrier but Beth is not?
(Since cystic fibrosis si caused by a , Beth and Tom's siblings who have CF must be ) Therefore, each parent must be a . Since neither Beth nor Tom has CF, this means they each have a chance of being a carrier. If they are both carriers, there is a chance that they will have a child with CF. If a test proves Tom is a carrier and Beth is not, there isa % chance that they produce a child with CF.
Joan was born with six toes on each foot, a
dominant trait called polydactyly. Two
of her five siblings and her mother, but not her father, also have extra
digits. What is Joan’s genotype for the
Joan's genotype is because the allele for polydactyly is to the allele for five digits per appendage. Because Joan's father does not have polydactyly, his genotype must be , therefore Joan, who does have the trait, must be .