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My husband is colour blind and we recently had a baby girl. I knowthat colour blindness is an X-linked recessive trait and that oneX-chromosome is randomly switched off in females because femaleshave two X-chromosomes and only need one. Does this mean that ourdaughter, as a carrier, could be colour blind in one eye or in someof her cone cells but not all of them?

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Casey Durgan
Casey DurganLv2
29 Sep 2019
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Related questions

. A recessive allele on the X chromosome is responsible for red-green color blindness in humans. This means that females have two copies (since human females are XX) and males have one copy (since human males are XY). This is called a sex-linked trait. A red-green color blind male is genotype Xn Y. A normal vision male is genotype XN Y. For this problem, a normal vision woman whose father is color-blind marries a color-blind male. N= not color blind allele, n = color blind allele. Y = Y chromosome.

a. What is the genotype of the color-blind father? Why?

b. What is the genotype of the color-blind husband? Why?

c. What is the genotype of the normal vision woman? Why?

d. What is the probability that this couple will have a son that is color-blind?

e. What is the probability that this couple will have a daughter that is color-blind?

We have discussed how recessive phenotypes are more likely to be expressed in males if the corresponding gene is found on the X-chromosome. For example, one-type of colorblindness is caused by a recessive X linked allele, and this trait is much more common inmales than females. But we have also discussed how, in placental mammals, one copy of each X chromosome is randomly silenced in female cells (X inactivation). This raisessomewhat of a paradox. Why donҀ™t half of heterozygous females exhibit colorblindness just like hemizygous males that carry the recessive allele?

a.

Based on your under standing of Xinactivation in placental mammals, provide an explanation for why heterozygous females generally do not exhibit colorblindness despite the random silencing of one X chromosome.

b.How would your answer change if we were talking about a marsupial mammal (inwhich the paternally inherited copy of the X chromosome is inactivated in every cell)? Would you expect half of heterozygous females in a marsupial species toexhibit color blindness? Why or why not?

1. If you had a fruitfly with phenotype A, what test would you make to determine if it was Aa or AA? Explain the different outcomes expected if the fly in question is AA or Aa.

2.The sex of birds, some insects, and other organisms is determined by a ZW chromosomal arrangement in which the males have like sex chromosomes (ZZ) and females are ZW (similar to XY in humans). Assume that a recessive lethal allele on the Z chromosome causes death of an embryo in birds. What sex ratio would result in the offspring if a cross were made between a male heterozygous for the lethal allele and a normal female?

3.A recessive gene for red-green color blindness is located on the X chromosome in humans. Assume that a woman with normal vision (her father is color-blind) marries a color-blind male. What is the likelihood that this couple's first son will be color-blind?

4. One form of hemophilia is caused by a sex-linked recessive gene. Assume that a man with hemophilia marries a phenotypically normal woman whose father had hemophilia. What is the probability that they will have a daughter with hemophilia? (Note: In this problem, you must include the probability of having a daughter in your computation of the final probability.)

5. One form of hemophilia is caused by a sex-linked recessive gene. Assume that a man with hemophilia marries a phenotypically normal woman whose father had hemophilia. What is the probability that their first son will have hemophilia?

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