Chromosomes in the cell nucleus

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.

Diagram showing a chromosome and its DNA

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 genes. One chromsome was inherited from the organism's mother, and is known as the maternal chromosome, and the other chromsome in the pair was inherited from the organism's father, and is known as the paternal chromosome.

The 23rd pair is 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 sex chromosomes is a different shape. There is an X and also a Y chromosome. Males are referred to as XY.

Diagram showing strands of chromosomes and maternal/paternal inheritanceDiagram showing how male and female chromosomes form