Understanding the genetic factors influencing height can provide insights into human growth and development, potentially leading to better treatments for growth disorders. A recent study sheds light on why men are, on average, taller than women, identifying a key genetic contributor.
The study, published in the Proceedings of the National Academy of Sciences, analyzed genetic data from one million individuals. Researchers focused on the SHOX gene, known to be associated with height, which is present on both the X and Y chromosomes. The team investigated whether the SHOX gene's effect differed depending on whether it was located on the X or Y chromosome.
By examining data from three biobanks, researchers identified 1,225 individuals with missing or extra X or Y chromosomes. They discovered that an extra Y chromosome contributed more to height than an extra X chromosome. This supports the hypothesis that the SHOX gene has a greater impact when present on the Y chromosome.
The SHOX gene's location near the tip of the sex chromosomes is crucial. In women, one X chromosome is mostly silenced, but the region near the tip remains active, allowing SHOX to function. Men have a fully active SHOX gene on both their X and Y chromosomes, leading to a slightly higher dose of the gene compared to women.
This difference in SHOX gene dosage accounts for approximately 20% of the average height difference between men and women. While other factors, such as sex hormones and additional genes, also play a role, this finding provides valuable insight into the genetic basis of height variation. Understanding these genetic mechanisms can contribute to a broader understanding of human growth and development.