OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

A diploid cell contains 23 pairs of chromosomes. This is because diploid organisms, like humans, have two copies of each chromosome—one inherited from each parent. In humans, there are a total of 46 chromosomes, reflecting the 23 pairs. Each pair consists of homologous chromosomes that carry the same genes but may have different alleles. The diploid number is crucial for sexual reproduction, as it ensures that the gametes (sperm and egg) produced during meiosis have the haploid number of chromosomes (23), maintaining the species' chromosome number after fertilization.