Cancer genetics - family tree - image description

The image shows a female and male figure. A pair of genes is shown beside each figure. The female has two green genes shown side by side. The male figure has a green gene and a red gene shown side by side. The red gene is the gene mutation.

Below the female, two circles are shown. These are two eggs. Each egg contains a copy of one of the female’s genes.

Below the male, two ovals with tails are shown. These are two sperm. Each sperm contains a copy of one of the male’s genes. One sperm contains the green gene. The other sperm contains the red gene mutation.

Lines travel down from each egg and sperm to four child figures. The lines show which genes have passed from an egg and a sperm to each child. Four possible combinations of genes can be made using one of the eggs and one of the sperm.

Two of the children have two green genes. They have a copy of a green gene from one of the eggs and a copy of the green gene from the sperm. Two children have a green gene and a red gene mutation. They have a copy of a green gene from one of the eggs and a copy of the red gene mutation from the other sperm.