Cell division

Chromosomes carry genetic information in a molecule called DNA.

A type of cell division called mitosis ensures that when a cell divides each new cell produced has the same genetic information.

DNA exists in a cell's nucleus within structures called chromosomes. Each section of a chromosome that contains the code for the production of a particular protein is called a gene.

A diagram showing the chromosomes and DNA and how they are structures

Each chromosome is made from a single molecule of DNA, but when a cell is ready to divide, the DNA copies itself, then coils and condenses to form the chromosomes that we see in micrographs.

Chromosomes carry genetic information in a molecule called DNA.

Each human body cell contains 46 chromosomes. These can be arranged into 23 pairs.

Each chromosome in a pair carries the same types of genes. The 23rd pair are the sex chromosomes:

  • In females, the two chromosomes are identical in shape. There are two X chromosomes. Females are referred to as XX.
  • In males, one of the chromosomes is a different in shape. There is an X and also a Y chromosome. Males are referred to as XY
Diagram showing how male and female chromosomes form