Question

Women have sex chromosomes XX, and men have sex chromosomes XY. Which of a woman's grandparents could not be the source of any of the genes on either of her X chromosomes?



mother's father



father's mother



mother's mother



father's father

Answer 1

The father's father donates only the Y chromosome, not the X chromosome. The father's mother gives him his X chromosome.

Therefore, the father's father does not pass on any of the genetics of his X chromosome

Answer 2

Answer:

Option). Father's father.

Explanation:

Humans are diploid organisms having 23 pairs of chromosomes (46 chromosomes). The 22 pairs of chromosomes are similar in both male and female, while the 23rd pair of chromosomes in male has one X and Y chromosomes and 23rd pair of  chromosomes in female has two XX chromosomes.

During reproduction, a man provides Y chromosome to his son and X chromosome to his daughter, while female provides X chromosomes to son and daughter.

Hence, the father's father of a woman would provide only Y chromosome to his son (woman's father), which could not be a source of any X chromosome's gene of that woman.

Thus, the correct answer is option). father's father.