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Biology · Paper 2 · Foundation + Higher · B6

Sex chromosomes and inheritance

Key ideas1 of 3

The usual chromosome pattern

Ordinary human body cells usually contain 23 pairs of chromosomes, 46 in total. One pair is the sex chromosomes. In the standard GCSE model, female sex chromosomes are XX and male sex chromosomes are XY.

An XX egg parent and XY sperm parent produce XX, XY, XX and XY combinations in the standard sex chromosome model.

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Practice, downloads and sources

Daily 5 · Exam practice · Revision sheet ↓

Foundation + Higher · B6. Fourteen core lessons, followed by two labelled Higher Tier lessons.

AQA Combined Science Trilogy 8464 · 4.6.1.6. Original notes, questions and diagrams. Models are simplified; teaching data are illustrative.