Download Genetics Beyond Mendel Practice Problems: Two rough black

Genetics
Beyond Mendel Practice Problems:
1.
Two rough black guinea pigs bred together, have two offspring, one of them
rough white and the other smooth black.
a. Determine the genotype of the P1 generation.
b. If these same parents were again bred together, what offspring in
proportions would you expect from them?
2. In parrots, gray color (G) is dominant over green (g). A second gene determines
how dark the base color is (whatever the base color is: gray, green, or
something else). The dark allele (D) is incompletely dominant over the light (d)
allele, so that a bird with the Dd genotype has a medium-intensity color. What
would a bird look like that had the genotype ggDD? What would a bird with the
genotype GgDd look like? What genotype(s) would a light green bird have?
3. If you mated a light green parrot with a purebred dark gray parrot, what would
the babies look like?
4. Suppose you took two of the baby parrots from the cross mentioned in question
#8, and you crossbred them. How many kinds of offspring would you get, and in
what proportions?
5.
Racoons have rings around their tails and a habit of washing their food in water
before eating it. Suppose that both of these traits are controlled via incomplete
dominance so that wide bands on the tail are BB, medium sized bands are Bb,
and narrow bands are bb and that washing all their food is WW, washing some
of their food is Ww, and washing no food is ww. How many of each genotype
will be in the F1 generation resulting from a cross of two racoons, both with
medium sized tail bands and that wash some of their food (assume 16)
6. A very common phenotype used in questions about codominance is roan fur in
cattle. Cattle can be red (RR = all red hairs), white (WW = all white hairs), or roan
(RW = red & white hairs together). A good example of codominance. (the
picture below is a bull with red and white)Yet the polled condition ”P” (hornless)
is completely dominant to the a horned “little p” condition. A polled roan bull
bred to a horned white cow produces a horned roan daughter. If this daughter
is bred to a heterozygous polled roan bull, what offspring may be expected?
(Order your genotypes horns first then coat color second) Could the same result
be expected from a cross between a polled roan PpRr cow and a polled white
Pprr bull? Make sure that you show your work!
7.
In gnus, the gene G controls an even disposition, and its recessive allele, g,
controls a bad disposition. Thus, there are good gnus (G-) and bad gnus (gg).
A lethal gene, d, kills the developing gnu while it is still an embryo. Thus, the
genotype dd would represent no gnus. Two good gnus, each of the genotype
GgDd, are mated. Their first offspring is born, and the zoo keeper speculates on
the probability that it possesses exactly the genotype of its parents.
a. What probability percentage would you give him?
b. There is a third gene of interest in gnus, skin texture, which follows
incomplete dominance. The phenotypes are smooth (SS), jagged
sandpaper (PP) and the heterozygous condition is rough (it feels like the
painted concrete walls within your school) What would occur if a tolerant
male gnu that is heterozygous for all three characteristics (he was
genetically tested) was crossed with a female that is bad tempered with
sandpaper skin. ( a coarse person, in all aspects- haha)
i. If they mated and two of their offspring died in utero, what are the
genotypes of the P1 generation?
ii. What is the probability of the above cross not producing a baby in
their next mating?
iii. What is the probability of producing baby gnus with good
dispositions and rough skin?
8.
In poultry, rose comb and pea comb patterns are produced by the dominant
effect of two different genes. The recessive nature of both these alleles
produces single comb. But in the cross between rose combed and pea
combed fowls, a new type known as walnut was also produced along with rose,
pea, and single in a 9:3:3:1 ratio.
a. What is the type of heredity used in this example?
b. What are the genotypes of the P1 generation?
c. If four walnut hens are crossed to a single combed male rooster and each
produces a large number of chicks. The first produces only walnuts, the
second produces only walnuts and peas, and the third produces only
walnuts and rose and the fourth produces among other types single also.
Give the genotypes of each of the four walnut hens.