X-linked Inheritance Consider this imaginary animal, the tree rat. They are usua

Question

X-linked Inheritance

Consider this imaginary animal, the tree rat. They are usually black, but sometimes they can be purple. The allele for the purple color is X-linked. You manage to capture two of these animals from the same family, a black female and her purple male offspring.

Question 5:

What is the genotype of the black female mother?

Question 6

Do you know the phenotype of the father based on the male offspring? Why or why not?

Question 7: (2pts)

Performing Monohybrid Crosses AP2

X-linked Inheritance

1. Next you breed the tree rats to each other (inbreeding is acceptable in this case). What percent of the offspring do you expect to be purple? Are any of them female? Use a Punnett square to show your work. [Use the letters B (black) and b (purple) to represent the alleles.]

2. What is the genotype of the black female mother?

3. Do you know the phenotype of the father based on the male offspring? Why or why not?

4. Next you breed the tree rats to each other (inbreeding is acceptable in this case). What percent of the offspring do you expect to be purple? Are any of them female? Use a Punnett square to show your work. [Use the letters B (black) and b (purple) to represent the alleles.]

Explanation / Answer

1. Next you breed the tree rats to each other (inbreeding is acceptable in this case). What percent of the offspring do you expect to be purple? Are any of them female? Use a Punnett square to show your work. [Use the letters B (black) and b (purple) to represent the alleles.]

XBXb x XbY

Xb

Y

XB

XBXb (Black female)

XBY (Black male)

Xb

XbXb (purple female)

XbY (purple male)

50% offsprings are purple

50% of females are purple

Question 2:

What is the genotype of the black female mother?

Xb=purple

XB= Black

In X linked inheritance whenever a dominant allele is present either in heterozygous or homozygous condition it is expressed. Since males are heterozygous they express whichever the allele they carry.

genotype of the black female has to be XBXb

genotype of the black female mother could XBXb or XBXB

Question 3

Do you know the phenotype of the father based on the male offspring? Why or why not?

No, since the X chromosome is inherited through mother we would not know the phenotype of the father.

Since the genotype of the mother is XBXb, then the father’s genotype could be either XbY or XBY

Xb

Y

XB

XBXb (Black female)

XBY (Black male)

Xb

XbXb (purple female)

XbY (purple male)

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