The sex chromosomes bear alleles for traits, just like the other chromosomes in
ID: 63284 • Letter: T
Question
The sex chromosomes bear alleles for traits, just like the other chromosomes in our bodies. Genes that occur on the sex chromosomes are said to be sex-linked. More specifically, the genes present on the X chromosome are said to be X-linked. Many more genes are present on the X chromosome than are found on the Y chromosome. Nonetheless, those genes found on the Y chromosome are said to be Y-linked.
The Y chromosome is smaller than its homologue, the X chromosome. Consequently, most of the loci present on the X chromosome are absent on the Y chromosome.
In humans, color vision is X-linked; the gene for color vision is located on the X chromosome but is absent from the Y chromosome.
Normal color vision (XN) is dominant over color blindness (Xn). Suppose a color-blind man fathers the children on a woman with the genotype XNXN
a) What proportion of their sons will be color-blind? (Another way to think of this is to ask: What are the chances that their sons will be color-blind?)
b) Explain how a color-blind daughter might result from this couple.
Explanation / Answer
A) no chances of colourblind son..as mother has normal vision withXNXN
B)if mother has genotypeXNXn then daughter becomes clour blind other wise daughter will carrier only
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