Login or Subscribe Newsletter. This photo represents the bell curve of women's and men's heights. It was created in by Linda Strausbaugh, professor of molecular and cell biology at the University of Connecticut. Greta Friar Whitehead Institute July 18, Lisa Girard Email: lgirard wi. Throughout the animal kingdom, males and females frequently exhibit sexual dimorphism: differences in characteristic traits that often make it easy to tell them apart.
In mammals, one of the most common sex-biased traits is size, with males typically being larger than females. This is true in humans: Men are, on average, taller than women. For example, women are much more likely to develop autoimmune diseases, while men are more likely to develop cardiovascular diseases. In spite of the widespread nature of these sex biases, and their significant implications for medical research and treatment, little is known about the underlying biology that causes sex differences in characteristic traits or disease.
This finding demonstrates a functional role for sex-biased gene expression in contributing to sex differences. The researchers also found that the majority of sex biases in gene expression are not shared between mammalian species, suggesting that — in some cases — sex-biased gene expression that can contribute to disease may differ between humans and the animals used as models in medical research. For example, if a tall parent passes on a gene associated with an increase in height to both a son and a daughter, but the gene has male-biased expression, then that gene will be more highly expressed in the son, and so may contribute more height to the son than the daughter.
The researchers searched for sex-biased genes in tissues across the body in humans, macaques, mice, rats, and dogs, and they found hundreds of examples in every tissue. They used height for their first demonstration of the contribution of sex-biased gene expression to sex differences in traits because height is an easy-to-measure and heavily studied trait in quantitative genetics.
Because height is so well studied, the researchers had access to public data on the identity of hundreds of genes that affect height. He found that sex-biased gene expression contributed approximately 1. Their database contains thousands of sex-biased genes. Slightly less than a quarter of the sex-biased genes that they catalogued appear to have evolved that sex bias in an early mammalian ancestor, and to have maintained that sex bias today in at least four of the five species studied.
