Question

in mice, the ability to run normally requires a particular protein. if either of the mouses alleles for that gene is the normal allele (r) then the mouse can run normally and is called “running”. if both alleles are mutant (r), so that the mouse lacks the particular protein, it causes mice to run in circles. mice with this phenotype are called waltzing mice. albinism is also inherited. brown hair (b) is dominant over albino (b). for each of the following crosses, draw a punnett square and answer the questions. 1. cross a heterozygous running, heterozygous brown mouse with a heterozygous running, albino mouse. a. what is the probability that an offspring will be running brown? b. what is the probability that a mouse will be running albino? c. what is the probability that a mouse will be waltzing brown? d. what is the probability that a mouse will be waltzing albino? 2. cross a heterozygous running, homozygous brown mouse with a waltzing albino mouse. a. what is the probability that an offspring will be running brown? b. what is the probability that a mouse will be running albino? c. what is the probability that a mouse will be waltzing brown? d. what is the probability that a mouse will be waltzing albino? 4. both parents are heterozygous for both traits. a. what is the probability that an offspring will be running brown? b. what is the probability that a mouse will be running albino? c. what is the probability that a mouse will be waltzing brown? d. what is the probability that a mouse will be waltzing albino?

Explanation:

Step1: Determine parental genotypes

For the cross of a heterozygous running, heterozygous brown mouse (RrBb) with a heterozygous running, albino mouse (Rrbb).

Step2: Find possible gametes

The first parent (RrBb) can produce gametes RB, Rb, rB, rb. The second parent (Rrbb) can produce Rb, rb.

Step3: Create Punnett - square

	RB	Rb	rB	rb
rb	RrBb	Rrbb	rrBb	rrbb

Step4: Calculate probabilities

a. Running brown (R - B -): There are 3 R - B - out of 8, so the probability is $\frac{3}{8}$.
b. Running albino (R - bb): There are 3 R - bb out of 8, so the probability is $\frac{3}{8}$.
c. Waltzing brown (rrB -): There is 1 rrB - out of 8, so the probability is $\frac{1}{8}$.
d. Waltzing albino (rrbb): There is 1 rrbb out of 8, so the probability is $\frac{1}{8}$.

Answer:

a. $\frac{3}{8}$
b. $\frac{3}{8}$
c. $\frac{1}{8}$
d. $\frac{1}{8}$