DNA is a molecule that contains an organism’s genetic information, which is passed on from one generation to the next. When a cell reproduces, it copies its DNA almost exactly.
In human reproduction, half of the DNA comes from the father and half from the mother. This is why you share many characteristics with your parents.
DNA has the famous double helix structure, shown in the picture above. Each molecule is made up of 4 chemicals called bases: adenine, cytosine, guanine and thymine, which are sometimes abbreviated to A, C, G and T.
DNA is found in all known living organisms, from complex animals like chimpanzees and humans, to single-celled organisms like plankton in the oceans.
The same 4 bases occur in the DNA molecules of all these types of organisms. Also, the A, T, G and C bases always occur in a similar sequence from one end of the DNA molecule to the other. This is evidence that humans are related to every other species on Earth.
The genes of organisms that look very different are surprisingly similar. For example, human DNA sequences are over 95% identical to chimpanzee sequences and around 50% identical to banana sequences.
You have to go back in time a long way to find a common ancestor between humans and bananas, but ultimately they have both emerged from the same family tree, the tree of life, and that is why they share common characteristics.