IN full, DNA is deoxyribonucleic acid. It is a chemical found in genes. It is these genes in turn that give humans their features: Tall, short, black or light complexion, long hair, big teeth, etc.

DNA is found in each and every single cell of the human body.

In females these genes take an XX formation and in males an XY.

In sexual interaction between a man and woman, these genes, in this case sperm and egg, mix. Some genes are more dominant than others in that they express themselves more powerfully than others.

It must be borne in mind that humans are 99.9 per cent identical; it is just 0.1 per cent that is different. In the case of identical twins, they are 100 per cent identical.

DNA tests are carried out to identify just 0.1 per cent of an individual’s features.

What this means is that human features are predominantly the same, and that the difference in these features is very slight.

Thus the process of DNA tests is all about taking human tissues of relatives and comparing their sequence. To determine whether the people under study have tissues with a common sequence. If they the people involved are related, their genes are similar.

As in all sciences, it is always a question of probability, because we are dealing with merely 0.1 per cent of the genes.

The reason why we turn to mothers in DNA tests is because they give birth. It can be ascertained that women give birth, unlike men. It is better to start off the DNA test with maternal relatives because the X gene is constant. As aforesaid, female offspring produce the X gene that is constant and runs throughout a family.

Maternal lineage is a sure one; if you have a brother and a sister, it is better to start with the sister in the case of a DNA test, because the X gene is constant in her.

The X gene runs in the entire family while the Y gene is limited in some instances to male offspring.