Question

“In human beings, the sex of a newborn child depends on the father and not the mother.” Justify this statement with the help of a flow diagram.

Hint:

Only the father’s sperm determines the sex because the mother only contributes X chromosomes.

Answer 1

Humans have 23 pairs of chromosomes, with one pair being sex chromosomes: Females have XX chromosomes, while males have XY chromosomes. The mother always provides an X chromosome via the egg. The father's sperm determines the sex: it can carry either an X or a Y chromosome. If the sperm carries X, the child will be XX (female). If the sperm carries Y, the child will be XY (male). \[ \text{Father (XY)} \xrightarrow{\text{produces}} \text{X-sperm or Y-sperm} \\ \text{Mother (XX)} \xrightarrow{\text{produces}} \text{only X-egg} \] Flow Diagram: \[ \begin{array}{c} \text{Sperm (X)} + \text{Egg (X)} \longrightarrow \text{XX (Girl)} \\ \text{Sperm (Y)} + \text{Egg (X)} \longrightarrow \text{XY (Boy)} \end{array} \] The child's sex depends on the sperm: X results in female, Y results in male. Therefore, the father determines the child's sex.