Images Dated 4th March 1998

Artwork of human fertilisation and implantation

Fertilisation and implantation. Artwork of the first week of human life, from egg fertilisation to embryo implantation in the uterus (womb). At lower left the ovary (white) releases a round egg into the fallopian tube (pink). Sperm reaches the egg & fertilises it 12-24 hours after egg release. The egg divides (upper left) into a two-celled embryo after 30 hours; at 3 days the embryo (called a morula) is 16 cells (top centre); at 4 days the advanced morula (centre right) nears the womb. At 4.5 days it is a blastocyst (hollow ball of cells) that enters the womb; at day 6 it im- plants on the womb, the thickened region forming the embryo and the placenta which will nourish it

© DAVID GIFFORD/SCIENCE PHOTO LIBRARY

Cultured cress seedlings

Plant genetics research. Silhouette of Thale cress plants, Arabidopsis thaliana, growing in a culture medium. The roots (lower frame) have fine root hairs growing horizontally out of them, which help to anchor the plant and absorb water and nutrients. Leaves are growing on the stems in upper frame. A. thaliana is mainly used as an international plant standard for genetic research. This is because of its short generation time, high seed production, small genome (genetic sequence) and ease of genetic manipulation. Research into A. thaliana is vital for improving our understanding of crop plants. The culture medium provides the plant with the nutrients it needs to survive

© DAMIEN LOVEGROVE/SCIENCE PHOTO LIBRARY