Images Dated 14th March 2003

Electrophoresis of RNA

Liver RNA. Electrophoresis gel containing RNA (ribonucleic acid) isolated from liver tissue. The RNA molecules (white bands) are being observed under ultraviolet light, which causes a chemical present in the gel to fluoresce. Electrophoresis separates molecules according to their size, by applying an electrical current to samples loaded onto the gel. The bands present in each sample represent different types of RNA. RNA is a nucleic acid that is involved in directing protein synthesis. Different RNA sequences are present in different tissues, representing differing patterns of gene expression

© PASIEKA/SCIENCE PHOTO LIBRARY

Beluga whales

Beluga whales (or white whales, Delphinapterus leucas). In summer, belugas migrate into river estuaries, where they moult. The yellowish colour of the males in this picture is typical of moulting adults. Belugas are normally a creamy white. Their skin is 100 times thicker than a human's, mainly for insulation. To encourage shedding of the old skin, they roll on the river bottom to rub against rocks and mud. Belugas inhabit the Arctic coastal waters of Europe, Asia and North America. They live in pods (groups) of 20-200. They dive to the seabed to feed on bottom- dwelling fish and invertebrates. Photographed in July in Cunningham Inlet, Canadian Arctic

© DOUG ALLAN/SCIENCE PHOTO LIBRARY