What is a chromosome?
In GCSE biology, a chromosome is a molecule found in the nucleus of a cell which contains genetic information in the form of DNA. Each chromosome carries multiple genes, short sections of the genetic code that contain instructions for building proteins. Chromosomes are passed from parent to offspring, allowing characteristics to be inherited.
In humans, each body cell contains 23 pairs of chromosomes, giving a total chromosome number of 46; human cells containing 46 chromosomes are said to be diploid. Sex cells in humans (egg cells and sperm cells) have a chromosome number of 23, and are described as haploid.
Chromosomes become visible only during cell division. The DNA is replicated, at which point the chromosomes take on a characteristic ‘X’ shape before being allocated to new daughter cells.
Chromosome revision resources to ace your exams
You can explore chromosomes further using our GCSE revision notes, topic questions and flashcards for your specific exam board:
Meet all your GCSE biology revision needs using our revision resources linked below. This includes revision notes, videos, flashcards and exam questions with student-friendly mark schemes.
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