So how does this work exactly? Why do men get MPHL more often than women? It isn't as simple as color-blindness or hemophilia. It can also occur in females but this is rare. This common type of baldness generally occurs in males. The kind of balding we're talking about is male-pattern hair loss (MPHL). There does seem to be an important gene on the X chromosome that causes men to bald early in life. And they’re not the only ones! Via Shutterstock Balding is not a simple trait Genes on both the X and the Y chromosome are important for “male” traits to develop. Well, this is certainly true of most of these conditions. So they suffer more often from these recessive traits than females do.
Men only have one copy of these genes because they only have one X chromosome. And why they also go bald more often.Īll of these traits come about because of a recessive gene on the X chromosome. And why they also get hemophilia, a blood clotting disorder, more often and they suffer worse from fragile X syndrome.
Which explains why males tend to be colorblind more often. If the eye color gene were on the X chromosome, men would have blue eyes more often. So what this means is that it only takes one recessive gene on the X chromosome to see a recessive trait in males. This means that they only have one copy of all of the genes on that chromosome. The other important consequence of being male is that males have only one copy of the X chromosome. The SRY gene, which is on the Y chromosome, turns on a bunch of other genes that cause the male reproductive system to develop.
Anyone who gets one working copy of this gene looks like a male. So becoming male is due to the dominant gene SRY. These people develop as female (although with some differences from an XX female). And there are cases where someone has an X and a Y chromosome but the SRY gene doesn't work properly. These people develop as male (although with some differences from an XY male). There are rare cases where someone with two X chromosomes also has an SRY gene. This gene tells a fetus to develop male body parts. There is a gene on the Y chromosome called SRY. And second, males have only one copy of all of the genes on the X and Y chromosomes. This means a couple of things.įirst, there is something about having the Y chromosome that makes a male a male. X and Y ChromosomesĪs you probably already know, males have an X and a Y sex chromosome and females have two X chromosomes. Let's now see how it applies to being male. Okay, now we understand dominant and recessive. But to have blue eyes, both copies need to be blue. You only need one of your copies to be the brown kind to have brown eyes. This gene comes in two forms - brown or blue. If both copies need to be the same to have a certain trait, then the trait is recessive.įor example, a big part of eye color is determined by the OCA2 gene. If you only need one copy of a gene version to get a trait, then it is dominant. These versions can be either dominant or recessive. And these genes come in different versions, which are called alleles. Remember, we have two copies of most of our genes - one from each parent. Let's quickly go over what dominant and recessive are to make sure we're on the same page. And there are plenty of other male-associated traits that are controlled by genes on other chromosomes as well. But many of the special problems males have are because of recessive genes on the X. Becoming a male is due to a dominant gene on the Y chromosome.