Name:___________________________
DIHYBRID INHERITANCE - Worksheet #2
In these crosses two pairs of alleles are involved.
1. In cattle, polled (P) (hornless) is dominant over horned (p), and black (B) is dominant over yellow
(b). What will be the condition of the offspring from several matings of homozygous polled black
bulls with horned yellow cows? When these F1’s are permitted to inbreed (mate with one another)
and form a considerable number there are 18 polled black cattle, how many horned black should
there be, assuming the ideal ratio?
2. A solid-colored, short-haired female rabbit (ssLL) is mated to a spotted, long-haired male (SSll).
The F1 offspring are allowed to interbreed and 64 offspring are produced. How many will be
expected to be spotted with long hair? How many solid-colored and short-haired?
3. Red polled shorthorn cattle have the genotype (RRPP) and white horned cattle have the genotype
(rrpp). Remember that when red and white cattle are mated the offspring are roan (Rr). Give the
genotype of the offspring resulting from a cross between a homozygous red, horned bull and a
homozygous white, polled cow. If these offspring could be bred many times in order to produce 16
offspring, what would be the phenotypes?
Name:___________________________
4. In some dogs, barking when trailing is due to dominant gene (B); others do not bark (b). Also erect
ears (E) are dominant to drooping ears (e). By crossing a heterozygous erect-eared barker with a
droop-eared silent trailer, what kind of pups could you expect?
5. A drug, phenylthiocarbamide (PTC), can be tasted by about 70% of American people; others cannot
taste it at all. Those who can taste it are called “tasters.” Those who cannot taste the drug are said to
be taste-blind. Tasters have a dominant gene for the trait whereas those who cannot taste the drug
have a recessive gene. An albino man who is a taster and has a taste-blind mother, marries a
normally pigmented taste-blind woman whose father is an albino taster. What is the genotype of the
man? Of his wife? Of her father? What types of children might the couple expect?