You've probably heard people say that if your mother's father was bald you're more
likely lose those beautiful locks of hair down the road. But what truth is there
to this? It turns out that one of the major contributors to hair loss is sex linked.
Humans have forty-six chromosomes of DNA, of which two help determine your
sex, the "X" and the "Y" chromosome. If you're a female you have two "X" chromosomes, but
if you're a male you have an "X" and a "Y" chromosome. Studies show that the
most influential hair-loss gene is located on the "X" chromosome only. What
does this mean? Well if you're a male you get an "X" chromosome from your mother, but must
receive a "Y" chromosome from your father. Because if you got your father's
"X" chromosome you would be a female. So if one of your mothers "X" chromosomes has this hair loss
gene
you have a 50/50 chance of getting it from her. In this way, hair loss is
partially hereditary and passed through the maternal side for males.
Females, on the other hand must get two copies of this gene, one on each "X"
chromosome in order to physically express it. So if your mother does
express these traits it means you will be passing an affected "X" chromosome to
you.
But why do we say to look at your mother's father? Well, if he has visible
male pattern baldness then your mother has at least one copy of the affected "X"
chromosome from him, because in order to have a daughter he must have passed on
his "X" chromosome, not his "Y". The thing to note here is that this is just one of
the contributors to hair-loss and while its thought to be the most significant, many
studies have found other hair linked genes which aren't sex linked at all.
Including some on the "Y" chromosome,
meaning they can be transferred from both the mother and the father.
On top of this, some studies have shown correlations between age, exercise
nutrition and even stress levels. So while a quick check of your mom's dad's
hair maybe an indicator for future hair loss, a head full of hair on Grandpa's head
does not guarantee you are in the clear.
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