# Explain why two children from the same biological parents can have different characteristics from each other.

> AQA A-Level Biology (7402) — 3.4.1 DNA, Genes and Chromosomes · Explain · 5 marks

> Each human body cell contains 23 pairs of chromosomes. During sexual reproduction, each parent passes on one chromosome from each pair to their offspring.

## Mark scheme (5 marks)

1. Chromosomes are inherited from both parents (one from each parent per pair)
2. Each chromosome carries genes / alleles that determine characteristics
3. Gametes are formed by a process that produces cells with different combinations of chromosomes
4. Fertilisation is random, so different combinations of alleles are inherited each time
5. Each child therefore inherits a unique / different combination of alleles, producing different characteristics

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