Question

15. The gene for petal color in a flower has incomplete dominance, so that individuals with two Al alleles (AIA) are red, individuals with two A2 alleles (A2A2) are white, and individuals with one of each allele (AIA2) are pink. In a cross between a red flower and a white flower, what is the probability of getting a pink offspring? (2 points) In a cross between a red flower and a pink flower, what is the probability of getting a pink offspring? (2 points) In a cross between two pink flowers, if there are two offspring, what is the probability of getting one red offspring and one pink offspring? (2 points) In a cross between two pink flowers, if there are two offspring, what is the probability of getting one red offspring and one white offspring? (2 points) In a cross between two pink flowers, if there are nine offspring, what is the probability of getting exactly three pink offspring? (2 points) 16. Two individuals that are heterozygous for a recessive autosomaltrait have an offspring with dominant phenotype. What is the probability that that offspring is a carrier (heterozygote?) (3 points) If that offspring has an offspring with an individual with the recessive condition, what is the chance their offspring has the condition? (2 points) 17. Most randomly occurring mutations that occur in humans do not have an effect on phenotype. Why is this? (4 points)

Answer 1

Representation:

A1A1 = Homozygous dominant= Red

A1A2 = Heterozygous = pink

A2A2= recessive = white

Cross 1: Red x White

A1A1 x A2A2

	A2	A2
A1	A1A2	A1A2
A1	A1A2	A1A2

· All pink

Cross 2: Red x Pink

· A1A1 x A1A2

	A1	A2
A1	A1A1	A1A2
A1	A1A1	A1A2

Red: pink = 1:1

Pink = 1/2

· A1A2 x A1A2

	A1	A2
A1	A1A1	A1A2
A2	A1A2	A2A2

· Phenotype ratio: Red: Pink: white = 1:2:1

· Pink = ½

Probability of 3 offspring to be pink = 1/2 x 1/2 x1/2 = 1/8

If total is 9, probability = 1/8 x 9 =9/8