ENIGMATIC REPTILIAN SEX RATIOS

Sex ratios.

Jennions et al. introduce the different kinds of sex ratio and their biology.

Distorting sex ratios.

D uring sperm production in mammals, the process of meiosis generates sper-matozoa that are genetically different but functionally equivalent. So, with respect to the sex chromosomes, for example, equal numbers of sperm are produced carrying either an X or a Y chromosome. Because X and Y sperm are equally capable of fertilizing an egg, equal numbers of male and female embryos are produced, and ...

Sex Determination, Sex Ratios and Genetic Conflict

Genetic mechanisms of sex determination are unexpectedly diverse and change rapidly during evolution. We review the role of genetic conflict as the driving force behind this diversity and turnover. Genetic conflict occurs when different components of a genetic system are subject to selection in opposite directions. Conflict may occur between genomes (including paternal-maternal and parentalzygo...

Sex ratios in primate groups

Changing sex ratios in diabetes.

A survey of sexes and ages in patients attending the Hartlepool diabetic clinic was carried out for the 20-year period 1948-67. The proportion of men aged 50 and over rose from 25.9% in the first decade to 38.2% in the second. An attempt has been made to explain this pronounced and rapid change.