In a family of eight (8) all the children are girls Which of the following reasons correctly explains this?

Analyze the question: A family has 8 children, and all are girls. We need to explain this using sex determination.

Concept: Sex determination in humans

• Females have two X chromosomes (XX). Males have one X and one Y (XY).
• The mother can only give an X chromosome in her egg, because she is XX.
• The father's sperm can carry either X or Y.
• The sex of the child is therefore decided by the father's sperm.

Step-by-step solution:

1. A girl is XX. She gets one X from the mother and one X from the father.
2. A boy is XY. He gets an X from the mother and the Y from the father.
3. For all 8 children to be girls, every child must have received an X from the father.
4. So the sperm that fertilised the egg each time carried the X chromosome.

Checking the options:

• A. Wrong. The woman always contributes X and does not determine the sex of the child.
• B. Wrong. Sperm count affects fertility, not the sex of the child.
• C. Wrong. If the Y chromosome were involved, the children would be boys.
• D. Correct. The father's X chromosome was involved every time, giving XX girls.

Exam tip: Remember "Father decides." The mother always gives X, so the father's sperm (X or Y) decides the sex. X from the father gives a girl, and Y from the father gives a boy. In reality, each pregnancy has about a 50% chance of either sex, so 8 girls in a row is unusual but possible by chance.