Images Dated 23rd October 2003

Alchemy

Alchemy. Historical artwork by the German artist Albrecht Durer (1471-1528) titled Melencolia I. It represents one of the four temperaments or humours, and it is thought that its title (ending in I) implies that Durer intended to draw the other three. Many of the artifacts seen, such as the mathematical "magic" square (upper right), balance (upper centre) and geometric shapes (far & lower left) are associated with alchemy. Alchemy was the pseudo-scientific predecessor to chemistry, which among other ideas is best known for its practitioners hunt for the Philosopher's Stone, which would impart eternal life and the ability to turn base metals into gold

© SHEILA TERRY/SCIENCE PHOTO LIBRARY

Mendelian inheritance

Mendelian inheritance in fowls, as a result of parental genes. P = parents, F & F2 = 1st and 2nd generation, D = dominant, R = recessive. Most inherited characteristics or traits are determined by multiple genes (sections of DNA), but some, such as colour in Analusian fowls, are governed by a single gene. These are known as Mendelian, named after Gregor Mendel the founder of genetics. The offspring of most plants and animals contain a mixture of genes from their parents. Certain genes are dominant over others, but if incomplete dominance (or blending) occurs then a new trait will result, in this case a grey colour. Mendelian traits occur in strict mathematical ratios

© SHEILA TERRY/SCIENCE PHOTO LIBRARY