Question

In mice, the ability to run normally is a dominant trait. Mice with this trait are called running mice (R). The recessive trait causes mice to run in circles only. Mice with this traitare called waltzing mice (r). Hair color is also inherited in mice. Black hair (B) is dominant over brown hair (b).For each of the following problems, determine the parent genotypes,determine possible gametes then construct a Punnet square to solve:
Cross a heterozygous running, heterozygous black mouse with a homozygous running, homozygous black mouse.

Parental Genotypes: _____

Phenotype of offspring: _____

Answer 1

Answer:

Parental genotypes: RrBb, RRBB

Offspring phenotype: Running and black hair

Explanation:

Given, Running (R) is dominant over waltzing (r)

Black hair (B) is dominant over brown hair (b)

Parent 1: Heterozygous running, heterozygous black = RrBb

Parent 2: Homozygous running, homozygous black = RRBB

When they mate ( RrBb X RRBB ) :

Gametes produced by RrBb = RB, Rb, rB, rb

Gametes produced by RRBB = RB

Offspring:

        RB          Rb         rB        rb

RB   RRBB    RRBb    RrBB    RrBb

All offspring mice will be running mice and will have black hair because all the four types of genotype at least have one dominant allele for both the genes.