Exploration of the human genome has progressed another step towards understanding the 24 human chromosomes. At least 505 disease loci can be mapped to chromosome 3, one of the largest in our genome. The annotated sequence, which has just been published in Nature (2006;440: 1194-8[Medline]), is likely to bolster research into several of these diseases, including spinocerebellar ataxia and von Hippel-Lindau syndrome, and into the medically important chemokine receptor group, whose genes are clustered in the short arm of the chromosome.

Individual susceptibility to depression depends on how we react physically and emotionally to everyday stress. To shed light on the interaction between genes and environment in our reaction to stress, researchers assessed stressors and mood in 275 pairs of female twins (170 monozygotic). They suggest that at least 12% of individual differences in reaction to stress can be attributed to genetic influences, while the remaining 88% could be explained by individual-specific environmental factors (Psychosomatic Medicine 2006; 68: 201-6).

There's a new variant of severe combined immunodeficiency in humans. Mutation in an enzyme, DNA ligase IV, had resulted in a dramatic reduction in B cell …