In mice, an allele for apricot eyes (a) is recessive to an allele for brown eyes (a ). At an independently assorting locus, an allele for tan (t) coat color is recessive to an allele for black (t ) coat color. A mouse that is homozygous for brown eyes and black coat color is crossed with a mouse having apricot eyes and a tan coat. The resulting F1 are intercrossed to produce the F2. In a litter of eight F2 mice, what is the probability that exactly two will have apricot eyes and tan coats

Explanation:

An allele for apricot eyes (a) is recessive to an allele for brown eyes (A).

An allele for tan (t) coat color is recessive to an allele for black (T) coat color.

A mouse that is homozygous for brown eyes and black coat color is crossed with a mouse having apricot eyes and a tan coat.

Parent genotype:   AATT     x     aatt

Gametes                  AT       x       at

F1 generation:                 AaTt

F1 parents:               AaTt    x     AaTt

Probability of having apricot eyes and tan coats: Probability of apricot eye:

  Aa  x Aa                      Probability of tan coat: Tt   x   Tt

 AA Aa aa where aa (apricot eye)-1/4               TT Tt tt where tt (tan coat)- 1/4

Probability of having apricot eyes and tan coats: 1/4*1/4 = 1/16.

probability that exactly two out of eight will have apricot eyes and tan coats- 0.0743

all matter is made up of atoms

in any element all atoms are the same

elements in a compound are always in a constant ratio: apex