Download Honors Biology Incomplete/ Co

Honors Biology
Incomplete/ Co-Dominance Worksheet 2
1. The lubber grasshopper is a very large grasshopper, and is black with red and yellow stripes. Assume that
red stripes are expressed from the homozygous RR genotype, yellow stripes from the homozygous YY
genotype, and both from the heterozygous genotype RY. What will be the phenotypic ratio of the F1
generation resulting from a cross of two grasshoppers, both with red and yellow stripes? What type of
inheritance is this?
2. Suppose you have two rose plants, both with pink flowers. You cross the two plants and are surprised to find
that, while most of the offspring are pink, some are red and some are white. You decide that you like the red
flowers and would like to make more. What cross would you perform to produce the most red flowered
plants? What type of inheritance is this?
3. Cattle have three colors. Red coat color,white coat in short horn cattle; with the heterozygous
condition producing the roan condition. A farmer has a roan bull and a red herd of cows. How can he
produce a pure breeding white herd, using only his present herd. Explain your answer.
4. In four O’clock flowers, red flowers (R) show incomplete dominance to white flower (R’). The heterozygous
condition produces pink flowers. Give the expected genotypic and phenotypic ratios for the offspring of a
cross between two pink flowering plants.
5. Suppose you identify a new gene in mice. One of its alleles specifies white fur color. A second allele
specifies brown fur color. Mice also are seen as white and brown patches. You want to determine whether
the relationship between the alleles is simple dominance (and if so which color is dominant) incomplete or
co-dominance. What sorts of genetic crosses would give you the answer? On what types of observations
would you base your answers? Name the type of inheritance.
6. In horses, coat color comes in many varieties. If a brown horse is crossed with a white horse, the offspring
are palominos (brown with white manes and tails). Name the type of inheritance. If a palomino horse is
crossed with a white horse, what will the phenotype ratio of the F1 be?
7. When roan cattle are mated, 25% of the offspring are red, 50% are roan, and 25% are white. Upon
examination, it can be seen that the coat of a roan cow consists of both red and white hairs. What kind of
inheritance is this? What were the original parental genotypes?