# Computing the probability of obtaining

1. You have three jars containing marbles, as follows:

Jar 1 : 600 red and 400 white

Jar 2 : 900 blue and 100 white

Jar 3 : 10 green and 990 white

If you select one marble from each jar at random, calculate the probability of obtaining:

a) Red, blue, green

b) 3 whites

c) Red, green, white

d) Red and 2 whites

e) A color and 2 whites

f) At least one white

2. Phenylketonuria (PKU) is a disease that results from a recessive gene. Two normal parents produce a child with PKU.

a. what is the probability that a sperm from the father will contain the PKU allel?

b. what is the probability thatan egg from the mother will contain the PKU allel?

c. what is the probability that their next child will have PKU?

d. what is the probability that their next child will be heterozygous for the PKU gene?

3. In cocker spaniels, solid coat color is dominant over spotted coat. Suppose a true-breeding, solid-colored dog is crossed with a spotted dog, and the F1 dogs are interbred.

a. what is the probability that the first puppy born will have a spotted coat?

b. what is the probability that, if four puppies are born, all of them will have solid coats?

c. what is the probability that, if four puppies are born, at least one of them will have a spotted coat?

4. cystic fibrosis is a disease caused by a recessive allel at a single gene. If two parents are both heterozygous for the disease allele, what is the probability of having at least one affected child in three births?

5. In Guinea pigs, fur length and fur color are controlled by two, unlinked genes. Long fur (L) is dominant to short fur (l), and brown pigmentation (B) is dominant to tan (b). In a digybrid cross (LlBb x LlBb),

a. what is the probability of observing a short-furred, tan individual?

b. what is the probability of observing at least one short-furred, than individual among one hundred progeny?

c. what is the probability of observing a LLbb genotype?

d. what is the probability of observing a Llbb genotype?