Images Dated 20th August 2002

Small intestine villi, SEM

Small intestine villi. Coloured scanning electron micrograph (SEM) of villi (folds) on the lining of the small intestine. Villi greatly increase the intestinal surface area for absorbing nutrients from food. The epithelium (outer layer, folded) of each villus contains enterocyte cells, which are involved in nutrient absorption, and goblet cells, which secrete mucus onto the intestinal surface. The inner villus tissue (not seen) contains blood vessels which transport digestive products to a nearby vein. Magnification: x27 at 6x7cm size

© SUSUMU NISHINAGA/SCIENCE PHOTO LIBRARY

Robot arm picks tray of DNA-containing bacteria

DNA cloning trays. Robot arm picking a tray of bacterial colonies which clone human DNA fragments for use in the Human Genome Project. The bacteria clone (replicate) the DNA as they reproduce, which allows workable amounts of DNA to be produced. The Human Genome Project aims to find the base sequence of all the genes in human DNA. Genes are lengths of DNA (deoxyribonucleic acid) which have specific functions within an organism. Human DNA is made up of over 100, 000 genes comprising some 3 billion pairs of bases. Once complete, the human genome map will allow for improved drug design and a greater understanding of genetic diseases. Phot- ographed at the Sanger Centre, Cambridge, England

© DAVID PARKER/SCIENCE PHOTO LIBRARY