Ten facts from the Human Genome Project

These facts reflect opinion in 2001 and might not reflect current knowledge

1) There are between 30,000 and 40,000 genes in the human genome.

Some previous estimates suggested there could be 100,000 or more human genes.

2) A human being can be made from a gene count only twice as great as that of a fly or worm.

There are 26,000 genes in the plant thale cress; 18,000 in the nematode worm; 13,000 in a fruitfly, 6,000 in yeast, and 4,000 in the tuberculosis microbe.

3) We are not fruitflies or worms because some our genes work differently – we have more “control genes.”

As we trace the increase of complexity from single cell creatures, through small animals like worms and flies, and up to us, what we appear to be adding is control genes. Evolution is not so much adding new genes performing wholly new functions – what it’s chiefly doing is to increase the variety and subtlety of genes that control other genes.

4) Hundreds of genes appear to have come from bacteria – one of which has been associated with depression.

We don’t understand the mechanism of transfer, and indeed it’s possible that the bacteria have picked up our genes rather than the other way round – though this seems less likely. But either way it’s a tremendous reminder of the unity of life, and of the fact that we don’t live in a cocoon isolated from other species.

5) Most mutations occur in males.

It’s about a two-fold difference. One suggested reason is the larger number of cell divisions in the male germ line (sperm).

6) More than one million SNPs have been identified.

Looking at the genetic differences between people – one variation every 500 to 1,000 bases (letters) – will usher in a new era of personalised medicine. Currently more than 1.4 million of these variations, known as SNPs (single nucleotide polymorphisms) have been found. Overall, humans are 99.8% genetically similar.

7)The purpose of the 97% of “junk” DNA is being discovered.

We have got stronger hints than before that the repeat family called Alu may play some important function. We have always suspected that we couldn’t simply divide the genome into 3% of good stuff (genes) and 97% of junk. Here we are beginning to see some of the functions of the ‘junk’. Exactly as one would expect the junk has a function – rather more diffuse than the hard information carried by the genes, but nevertheless functional in some way. It may help to move genes around.

8) Just 483 existing “targets” in the body account for all the pharmaceutical drugs on the market.

The HGP and the SNPs research will provide thousands of extra “doorways” or destinations for new medicines and drugs to work on. Already new ways of tackling asthma, Alzheimer’s disease and depression are being looked at, using new genetic targets.

9) Understanding of how the body works is dramatically increasing due to HGP knowledge.

Apart from new drugs, the HGP research is pointing to a vastly increased knowledge of how the human body works – with better explanations now available for a range of conditions or biological responses.
One small example is that the mystery of bitter taste has been solved – a new family of proteins (which come from genes) that control this response have been found in taste buds.

10) Understanding of how we evolved as human beings is being rapidly advanced through “genetic archaeology.”

Genetic sequencing information is providing more evidence of how we diverged from monkeys 25 million years ago. What genetics is also clearly showing is our close relationship with other life forms.
In the words of John Sulston: “We are confirming Darwin – that is the most useful take home message from this. It is the unity of life, or Nature being conservative, or the idea of the Blind Watchmaker – the notion of evolution as a constant reworking or random recombining of parts.”

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