Last updated at 17:50 GMT, Thursday, 27 December 2012

Ancient viruses

A retrovirus

How have viruses helped humans to evolve?

The human body is made up of many millions of cells containing genes. Genes hold the information about how the body should grow and develop. If you have had a virus, it can be detected in your genes.

In this week's 6 Minute English William and Helen talk about how some ancient viruses have survived in our genes.

This week's question:

How many genes do human beings have?

a) between 10,000 and 25,000

b) between 100,000 and 250,000

c) between 1 million and 2.5 million

Listen out for the answer at the end of the programme.

Listen

Ancient viruses

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Vocabulary

genes

molecules in our body which tell our bodies how they should grow and develop

traces

small signs that something happened

a virus

a very small creature that spreads infectious diseases

an ancestor

a person or plant that is related to someone or something today but that lived earlier

to evolve

to change and adapt slowly over a long time

a micro-organism

a very small creature

to thrive

to prosper, to develop or live well

detection

noticing something