Quote from: Jamie-o on April 26, 2009, 03:19:24 AM
I thought it worked out that they could inherit it from the mother or the father, so it actually increased the likelihood of going bald.
This intrigued me, so I decided to look it up! Anyway, everything I've found says that the gene for male pattern baldness is a recessive gene that is carried on the X chromosome. This basically means that for FTMs the chances of becoming bald are lessened, from approximately 50% to 25%.
How this works is as follows (long technical description, feel free to skip it if you want, I won't be at all offended):
Generally, people have two chromosomes - XX or XY (I'm very aware that there are various other conditions that have a different configuration of chromosomes, but I have no idea how to apply this here I'm afraid, sorry). In cis-gendered people, XX = female and XY = male - for trans people, generally XX = FTM and XY = MTF.
So, someone who is born XX inherits one X from their mother and one X from their father; the X from their mother could be either of the two Xs that their mother has. Someone who is born XY inherits the X from their mother (again, it could be either of the two Xs) and the Y from their father.
Genes can be either dominant or recessive. A dominant gene will override a recessive gene - therefore, if someone inherits a dominant from one parent and a recessive from the other, the dominant one will be the one that shows. The only way that the recessive one will show is if it is inherited from both parents. So, if we use a capital letter to denote a dominant gene and a lower case letter to denote a recessive gene, the chances of inheritance of a characteristic looks a bit like this:
If the mother and father both have one dominant and one recessive gene (so neither show the recessive characteristic)
From mother: C or c
From father: C or c
Child: CC or Cc or cC or cc
Therefore, there is a 25% chance that the child will have the recessive characteristic. This is particularly obvious in eye colour, as brown eyes are dominant and blue recessive - however, two brown eyed parents can have a blue eyed child, as above.
Of course, the parents could equally be CC, or cc, or any combination of the above, but I won't go into all the possible permutations now.
This gets more complicated when the gene is carried on the X chromosome, as it then becomes linked to sex also. The pattern for inheritance then looks like this (B being the dominant gene i.e. NOT balding, b being the recessive gene leading to male pattern baldness):
Mother: BB
Father: B
XY - B or B
XX - BB or BB
Mother: Bb
Father: B
XY - B or b
XX - BB or Bb
Mother: bB
Father: B
XY - B or b
XX - BB or Bb
Mother: bb
Father: B
XY - b or b
XX - Bb or Bb
Mother: BB
Father: b
XY - B or B
XX - Bb or Bb
Mother: Bb
Father: b
XY - B or b
XX - Bb or bb
Mother: bB
Father: b
XY - B or b
XX - Bb or bb
Mother: bb
Father: b
XY - b or b
XX - bb or bb
Giving and XY child - 8 x B, 8 x b and an XX child - 4 x BB, 8 x Bb, 4 x bb. So, an XY child (cis gendered male or MTF) has a 50% chance of male pattern baldness, and an XX child (FTM) has a 25% chance.
Hope that makes sense - it's a lot for a Sunday morning!
Right, I'm off to the beach - laters!