Question

Male XX and female XY sometime such conditions occur due to

• A. Deletion
• B. Transfer of segments in X and Y chromosomes
• C. Aneuploidy
• D. Hormonal imbalance

Answer 1

Answer: (B)

Transfer of segments in X and Y chromosomes

Human follows XX- XY mechanism of sex determination in which females have XX sex chromosomes and males have XY chromosomes as their sex chromosomes.

The Y chromosome carries TDF gene that is responsible for the development of testis in human males absence of this gene in females determines feminism. Unequal crossing over between X and Y chromosomes during meiosis results in the transfer of TDF gene on X chromosome while the Y chromosome lacks it.

Fertilisation of sperm carrying Y chromosome without TDF gene with egg lead to the development of XY females as the Y chromosome does not have TDF gene so no testis formation. Similarly, fertilization of sperm with X chromosome carrying the TDF gene with egg lead to development of XX males as the X chromosome has TDF gene so male genital organs are formed.

Changes in chromosome number by additions or deletions of less than a whole set is called aneuploidy, but here chromosomal parts are exchanged.

Removal of one or more nucleotide bases to the DNA segment is known as deletion, it is a point mutation that alters the gene at molecular level.

Hormonal imbalance does not change the chromosomal constitution of organisms.

So, the correct answer is option B.