Name____________________
Period________
Different Types of Dominance
(some examples are true, some are made up)
1. When shorthorn red cattle are bred to shorthorn white cattle, they produce roan
(red and white hairs interspersed) offspring.
(a)What type of inheritance is this and how do you know?
(b) If two roan shorthorns are crossed, what is the probability of red, white and
roan colors in their offspring?
2. In the petunia, a pure breeding red flower is crossed with a white one to produce
pink offspring.
(a) What form of inheritance is this and how do you know?
(b) Show the genotypes of the parents and a cross between them with a punnett
square.
(c) If the offspring from part (b) bred with a homozygous red plant what would
their offspring look like?
(d) If the offspring from part (b) bread with a homozygous white plant what
would their offspring look like?
3. In andalusian fowl, BB is the gene for black plumage. bb is the gene for white
plumage. These genes show incomplete dominance. The heterozygous condition
results in blue plumage. In the following crosses, what percentage of the
offspring would we expect to be black, blue and white:
(a) black X blue
(b) blue X blue
(c) blue X white
4. Two carnations (flowers), a red one and a white one, are crossed and the
offspring can be one of three different genotypes. If this gene shows incomplete
dominance, what is/are the likely color(s) of the heterozygous plants?
5. On a fox ranch, a mutation arose that gave a “platinum” coat color that was very
popular with fur buyers. The breeders tried a couple of times to breed a pure
strain of platinum foxes; every time they bred two platinum foxes together, there
were some normal foxes in the progeny. For example, in repeated matings of the
same platinum foxes, 82 platinums and 38 normal offspring were produced. State
a concise genetic hypothesis to account for these results.
.
6. In dogs, gum coloration is co-dominant for black and pink. You have a lovely
spotted gummed Labrador retriever who has just had 8 pups. Four of the pups
have spotted gums like your dog, and 4 have pink gums. What is the likely
phenotype of the sneaky neighbor dog and what is your evidence?
7. A man with a large uni-brow and a woman with thin, small eyebrows have a
child. The child is born without a uni-brow but they do have thick bushy
eyebrows. If bushiness of eyebrows and unibrows are controlled by the same
gene, what sort dominance is most likely at play here and how do you know?
8. A desert tortoise is born with either a pale yellow tiled shell or a pale brown tiled
shell. The trait is controlled by co-dominance.
(a) If a yellow shell and a brown shell have offspring what might the young look
like? How do you know?
(b) What is the genotype of the parents and the offspring? Can you be 100%
certain (why or why not)?
9. Husky ears can be either floppy or straight. Two husky parents are both
homozygous for straight ears. They have one pup in a litter of 10 that has floppy
ears. How might this have happened? Explain your reasoning.
10. Two parents have 3 children with the following blood types. AB, A and B.
What do you know for sure about the parents’ blood types?
11. Two parents are heterozygous for typical hands. One of their three children has
webbed hands. How did this happen? Explain your reasoning.
12. Two homozygous, dominant red rainforest tree frogs mate. They lay 1/3 of their
eggs in fast moving water, 1/3 in an eddy near the shore and 1/3 in rain water
collected in a leaf. The young in the fast water all develop orange skin, the young
in the eddy develop orange and red skin modeled like a giraffe and those raised in
the leaf develop red skin.
(a) What might be going on? What is your evidence?
(b) What could you speculate about the parents?