Question

Red-green color blindness in humans is caused by a recessive allele located on the XX chromosome. Figure 1 shows the potential offspring of a female who is red-green color-blind and a male with full-color vision. All of the possible male offspring would be color-blind, and all of the possible female offspring would have full-color vision.

If during the production of male gametes an error in meiosis occurred, sperm containing both an XX and a YY chromosome could be produced.Figure 1. Possible offspring of a female who is red-green color-blind and a male who has full-color vision.
How would the extra chromosome affect the male offspring produced by the gamete?
A. None of the potential offspring would be male, because the potentially male zygote would have two XX chromosomes, and the YY chromosome would be ignored.
B.The male offspring would all be red-green color-blind, because of interference from alleles on the YY chromosome.
C.The male offspring would have full-color vision, because of the presence of the extra XX chromosome.
D.There would be no change to the phenotypes of the possible offspring, because the extra XX chromosome would not be active.

Answer 1

The answer will be B

Answer 2

The extra YY chromosome mentioned in the scenario would not affect the male offspring produced by the gamete, as the male sex is determined by the presence of a single Y chromosome.

Therefore, the correct answer is not listed in the options provided. However, we can say that the extra YY chromosome in a sperm would not produce a viable zygote when fertilized with an X-bearing egg, since there would be an incorrect number of sex chromosomes (XYY). This condition is called XYY syndrome and is not related to red-green color blindness.

In any case, the phenotype of the male offspring produced by the gamete would still be red-green color-blind, since they would inherit the X chromosome with the recessive allele for color blindness from their color-blind mother. The presence of an extra YY chromosome in a sperm would not change the expression of the color blindness gene on the X chromosome, as the YY chromosome does not carry that gene.