Genetics Study Guide (Page 4 of 5) in pdf

Genetics Study Guide Page 4

In central Kentucky there is a creature know as a wildcat. It comes in three colors, blue, white,

and light-blue. This trait is controlled by a single locus gene with incomplete dominance. A

homozygous (BB) individual is blue, a homozygous (bb) individual is white, and a

heterozygous (Bb) individual is light-blue. What would be the genotypes and phenotypes of the

offspring if a baby-blue wildcat were crossed with a white one?

Sex-Linked Traits

Coat color in cats is a codominant trait and is also located on the X chromosome. Cats can be

black, yellow or calico. A calico cat has black and yellow splotches. In order to be calico the cat

must have an allele for the black color and an allele for the yellow color. Use a punnett square to

show why there are no male calico cats. Remember to attach the alleles to the X chromosome (X

A female calico cat is crossed with a male black cat. What are the phenotypes of the offspring

and in what proportion.

Multiple Alleles

In humans there are four different blood types: A, B, AB, and O. The alleles for A (I

) and B (I

)

are codominant and the allele for O (i) is recessive. The genotype for a person with blood type A

could either be I

or I

i. Suppose a father of blood type A and a mother of type B has a child of

type O. What blood types are possible in their children?

Genetics Study Guide Page 4