What in genes decides your gender?

Question: What in genes decides your gender?
- Keywords:
  biology,
  gender,
  gene
Asked by harrystylesgirlfriend to Mike, Pip, Tianfu, Tim, Tom on 27 Jun 2012.
- Tom Lister answered on 27 Jun 2012:
  
  There is just one of 52 chromosomes that decides your gender as far as I can remember. This must influence the amount of androgen hormones your body produces at crucial stages of your life (like in the womb and during puberty).
  
  It’s not the same in all animals though. Many (like slugs) are both male and female, and some (like some birds) can become either male or female depending upon the temperature at which they are incubated!
- Philippa Bird answered on 27 Jun 2012:
  
  Ok, so basically you have 23 pairs of chromosomes (which are packages of DNA). You get one set from your mum and one set from your dad, and they do the same things but the genes in each pair have a bit of a battle for which one is “dominant”, so for example if your dad gives you brown eyes and your mum gives you blue eyes your eyes will be brown because the brown-eyed gene is dominant.
  Most of the pairs of chromosomes have the same shape and structure as each other, but for gender it’s a bit different. The last pair of chromosomes in the set of 23 determine your gender. They are named based on how they look, X and Y (The Y chromosome is a bit runty and is like a X without a leg). If you have two Xs you are female, and if you have an X and a Y you are male (it’s not possible to have two Ys, which will become clear in a minute).
  So, as all our mothers have XX, we will definitely get an X from her. All our fathers are XY, so we have a 50% chance of getting an X from him (meaning we will be XX and female), and a 50% chance of getting a Y (so we will be XY and male). On the Y chromosome, there is a gene called SRY (I like to call it the “sorry” gene), which is responsible for making a person male. Obviously females don’t have that so they are not male, there is no equivalent to the SRY gene on the X chromosome.
  
  Interesting fact – men are more likely to be colour blind than women. This is because the “colour blind” gene is on the X chromosome, but it is not dominant. That means that if a woman has a “colour blind” gene on one of her X chromosomes, and a “normal” gene on the other, the “normal” will override the “colour blind”. But if she then gives the “colour blind” chromosome to her son, there is no equivalent gene on his Y chromosome, so he will definitely be colourblind. If she gives the “colour blind” chromosome to her daughter, the daughter won’t be colourblind unless her dad is (ie his only X chromosone has the “colour blind” gene), which is much less likely.
  
  This is GCSE (or maybe A-level) stuff, I don’t know how old you are but sorry if it’s a bit complicated.
  Great question though, that kind of curiosity shows a scientific mind!
- Tim Stephens answered on 27 Jun 2012:
  
  Great answer, Pip.

Question: What in genes decides your gender?

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