Why we get cancer SCIENCE ORGANISED!

Scan page 11

various cancers, while our simpler relatives, the sponges and jelly-fish don't?

The answer, according to James Graham, writing in the Journal of Theoretical Biology, is simply that we have genes for cancer (oncogenes) while they But why do we have genes for cancer?

Graham observes that jellyfish have not evolved any of the complex organs found in the Bilateria*. They are very simpleorganisms with only a few types of cell. They are. extremely plastic in form and function. Turn a jellyfish inside out and the gut cells become skin cells and vice versa. Chop it up and the bits become new jellyfish. The cells are constantly growing and dividing.

Compared with Biateria, they have a relatively small amount of genetic material (DNA), and there is Little to go wrong with it.

The complex animals may Campaign for Gay Rights To join or affiliate, write to Chris Richardson, 21 Deyonshire Promenade, Lenton, Nottingham NG7 2DS. £5 for individuals, or for affiliated organisations, per 1000 • members; £Z IOW-wageu uP?- isiad ind ividuals, £1 unwaged also presents a threat to individual Bilaterians. Mutations caused by chemicals or radiation can cause some of the 99% of inactive DNA in a cell to become active, disrupting the order of the body. And the large total amount of DNA makes it certain that mutations are a common occurence.

Mutations occur in the simple animals, but are far less serious. Since a typical jellyfish cell does the same things as any other, a mutation would probably harm only the cell involved, rather than the whole animal.

As Bilaterians evolved in complexity, it was thererenewal of aged cells slows down after sexual maturity; wauy cells have stopped dividing and so cannot have cancerous offspring.

2. Avoiding mutagens (things that cause mutations) like sunlight. Early Bilaterians lived on the sea-bottom for 100 million years. Their descendants had opaque coverings of non-living material with pigmented skin that filtered out ultra-violet light. They were small, presenting less target for radiation, or lived in sheltered habitats.

3. Repairing damaged DNA.

Special enzymes (proteins that make or break chemical possesses. The arthropods lacked an immune system and had remain small with thicker, opaque, pigmented coverings. Many are restricted to sheltered places. They have shorter lives which lessens the time for cancers to appear.

The vertebrates developed a better and better immune system and could relax some other defences. Body coverings could be reduced in thickness, the body could grow larger and more complex. The ageing process could slow down, the age of sexual maturity and the bution from supporters.

I want to become a Socialist Ürganiser supporter/ I want more information.

Name Address Send to Socialist Organiser, 28 Middle Lane, London N8 8PL.

Scan page 12

Organiser no. 149 October 6 1983 masthead than for the SO