Genetics Problems Worksheet
1. In cattle, the hornless condition (H) is dominant and the horned condition (h) is recessive. A bull
without horns is crossed with a cow with horns. Of the four offspring, one (1) is horned and three (3) are
hornless. Determine the genotype of the bull and the cow.
Hh (bull) x hh (cow) = some offspring will be Hornless & horned. The number of offspring is
insignificant.
2. In humans, widow's peak (W) is dominant over a continuous hairline (w), and short fingers (F) are
dominant over long fingers (f). Two individuals with widow's peak and short fingers have a child with
continuous hairline and long fingers. Determine the genotype of the parents.
WwFf x WwFf
3. In humans, free ear lobes (E) is dominant over attached ear lobes (e), and brown eyes (B) is dominant
over blue eyes (b). A man with free ear lobes and brown eyes marries a woman with attached ear lobes and
brown eyes. Of four children, one has free ear lobes and brown eyes, one has free ear lobes and blue eyes,
one has attached ear lobes and brown eyes, and one has attached ear lobes and blue eyes. Determine the
genotypes of the parents.
EeBb x eeBb
4. In humans, hemophilia is a sex-linked condition and normal blood clotting (H) is dominant to the
condition of hemophilia (h). A woman with hemophilia marries a normal man. What are the probabilities
of them having children with hemophilia and their sexes?
XHXh x XHY…. H is normal, h is hemophilia (recessive)… no girls will have hemophilia, ½ chance that
their boys would have hemophilia
5. In humans, being right-handed (R) is dominant over being left handed (r), and normal vision is dominant
over color blindness (which is sex-linked). Two right-handed parents with normal vision have a son who is
left-handed and color-blind. Determine the genotypes of the son and both parents. What can you tell me
about the phenotypes of the parents?
RrXNY x RrXNXn
6. In horses, black coat color (B) is dominant over roan coat color (b), and a trotter (T) is dominant over a
pacer (t). A black trotter mare was bred with a stallion to produce a roan pacer colt. Determine the
genotypes of the colt and mare and all the possible genotypes for the stallion. Perform a cross between
each stallion genotype and the mare. Which is the higher probability for the stallion's genotype? BbTt x
bbtt has the highest probability – other choices: BbTt, bbTt, Bbtt
7. In guinea pigs, curly hair (H) is dominant over straight hair(h). Work out the F1 and F2 generations of a
cross between a homozygous curly haired guinea pig and a homozygous straight haired guinea pig. SHOW
ALL WORK! Include all possible genotypes and phenotypes. P = HH x hh= only curly.. Hh (F1) x Hh
(F1) = HH, Hh, hh (F2) Curly/straight
