R and S are hypothetical co-dominant X-linked traits that can be easily observed
ID: 151021 • Letter: R
Question
R and S are hypothetical co-dominant X-linked traits that can be easily observed. The phenotypes of each individual are indicated in the figure below. The male child in this pedigree indicated by the filled square has Klinefelter syndrome (XXY). Which is correct? ( I know the answer, please explain why)
RS RSR A. Homologous recombination in the mother B. Nondisjunction happened in the mother C. Nondisjunction happened but you cannot tell which parent D. Homologous recombination in the mother E. Nondisjunction happened in the fatherExplanation / Answer
The answer is nondisjunction happened in the father.
what is nondisjunction?
Nondisjunction means when homologous chromosomes and sister chromosomes fail to separate during anaphase I and II simultaneously. As a resultant, one gamete will be having duplicate copy or 2 copies of one chromosome and other will be having no chromosome.
Klinefelter syndrome is basically related to sex chromosomes means nondisjunction of sex chromosome. It is representated by XXY. It is an example of aneuploidy basically hyperaneuploidy where number of chromosome will be high in father.
Here R and S are co-dominant X linked traits means they are equally dominant and dominant gene is carried on X chromosome. The RS son receive XX and Y from father only, because of aneuploidy of fathers chromosome,
Thanking you
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