Download Genetics Problems - FW Johnson Collegiate

Genetics Problems
1. What kind of gametes, and in what proportions (ratio or percentage)
would the following individuals produce?
a. AA
b. Aa
c. aa
d. AABB
e. AAbb
f. AaBB
g. aaBb
h. AaBb
2. Some individuals can taste the chemical phenolthiocarbamide (PTC).
For these “tasters” the taste is very bitter. Others do not taste it.
Tasters married to tasters have mostly taster children, but also have
a few non-taster children. Tasters married to non-tasters have both
types of children. Non-tasters married to non-tasters always have
non-taster children.
a. Which condition is dominant and which recessive?
b. If a non-taster is married to a taster who had one non-taster
parent, what phenotypes and in what proportions would you
expect to observe in their children?
c. If two heterozygous tasters were married what would you
expect among their children?
d. If a non-taster were married to a homozygous taster, what
would you expect among their children?
3. A rooster with black feathers is mated to a hen of the same
phenotype. Among the offspring, 21 chicks are black and 8 are white.
What is the dominant gene? What are the parents genotypes?
4. Palomino horses are known to be caused by the interaction of two
different alleles. The allele “B” in the homozygous condition produces
a chestnut, or reddish-brown, horse. The allele “b” produces a very
pale cream coat colour, called cremello, in the homozygous condition.
The palomino colour is caused by the interaction of both the chestnut
and cremello alleles. What type of inheritance is at work in this
situation? Indicate the expected phenotypic ratio in the F1
generation from a mating between a palomino and a cremello.
5. A woman with blood type O and a man who has blood type AB are
expecting a child. What are the possible blood types of the child?
6. What are the chances of a woman with AB blood and a man with type
A blood having a child with type O? Support your answer.
7. In guinea pigs, black coat colour (B) is dominant to white (b), and short
hair length (S) is dominant to long (s). Assume that these traits sort
themselves out independently and indicate the genotypic and
phenotypic ratios for the following crosses. Hint – always start with
the genotypes of the parents and then determine the types of
gametes that are possible for each parent.
a. Homozygous for black, heterozygous short-hair guinea pig
crossed with a white, long hair guinea pig.
b. Heterozygous for black and short-hair guinea pig crossed with a
white, long-hair guinea pig.
c. Homozygous for black and long-hair crossed with a
heterozygous black and short-hair guinea pig.
8. In pigeons, checkered is dominant to plain. A homozygous plain female
is crossed with a checkered male whose mother was plain.
a. What would you expect to observe among the offspring?
b. Diagram the cross using appropriate symbols.
10. Dark hair (M) in humans is dominant over blond hair (m). Freckles (F)
are dominant over no freckles (f). If a blond, freckled man whose
mother had no freckles marries a dark-haired non-freckled woman,
whose mother was blond, what proportions of their children would be:
a. Dark haired and freckled?
b. Dark haired and non-frecked?
c. Blond and freckled?
d. Blond and non-freckled?