Sex Determination
Sex determination is the process by which the sex of an offspring is decided at fertilisation.
Practice This ConceptMain explanation
Teacher explanation
In humans, the mother has XX chromosomes and the father has XY chromosomes. The mother always contributes an X chromosome through the egg, while the father can contribute either X or Y through the sperm. If the sperm carries X, the child is XX and develops as female. If the sperm carries Y, the child is XY and develops as male.
Example
A human baby receives one sex chromosome from each parent. An X-bearing sperm produces a girl child, and a Y-bearing sperm produces a boy child.
Simple analogy
Mother gives X, father gives X or Y.
Common confusion
Students often think the mother decides the sex of the baby. That is wrong because the father's sperm can carry either X or Y.
Exam tip
Always write XX for female and XY for male in humans. Mention that the father's sperm determines the final combination.
Answer writing and exam use
1-mark use
Write the exact meaning of sex determination in one clean line.
2-mark use
Define sex determination and add one example or condition.
3-mark use
Explain sex determination, show the method or example, and mention the common mistake.
Practice this concept with focused MCQs
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