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By 18, somewhere along the line you’ve hopefully had some kind of science/biology class where they talked about dominant and recessive genes, Punnett squares, and all of that
But in case you didn’t, or it’s slipped your mind (honestly, given your age there’s a good chance they may have covered this while you were learning from home during the pandemic, so kind of understandable if you don’t remember) here’s a quick refresher
You get one copy of each gene from both parents. Sometimes you get the same version of them from each parent, sometimes you get a different version.
Let’s imagine there’s a single gene that determines if you’re going to be tall. There’s a tall version of that gene, that we’ll call “T” and a short version that we’ll call “t”
We’ll say that “T” is the dominant version, and “t” is recessive.
What that means is that if you carry the “T” gene, it will always be expressed. You’ll be tall as long as you have at least one copy of it.
Remember, you get one copy of this gene from each parent. They each also have 2 copies of this gene.
Your dad is tall, so he must be carrying at least one copy of the T gene. He might have one, or he might have two.
Your mom is short, so she doesn’t have the T gene, she has 2 copies of the t gene.
So if your dad has 2 copies, all of his children will be tall, because they’re all going to get a T from him.
But if he only has 1, he could have short children if he passes along his t gene instead, and since your mom doesn’t have a T to pass on, she can only pass on the t gene
We can illustrate this in something called a Punnett Square, which looks something like this (apologies for the lazy ASCII layout)
_ | T | T
t | Tt | Tt
t | Tt | Tt
or
_ | T | t
t | Tt | tt
t | Tt | tt
The top rows represent your father’s genes, with 1 or 2 copies of the T gene, and the column on the left represents your mothers with only the t gene
And the rest of the squares represent the possible combination of genes you can have.
So in this hypothetical, if your dad is a “Tt” and your mom is a “tt” you have a 50/50 shot of being tall.
This is a very simplified version of it. In reality, there’s not just one gene that determines height, there’s actually about 10,000 genetic factors that have some impact on your height.
And for shits and giggles, let’s imagine that both of your parents were tall so the punnet squares look like this
_ | T | T
T | TT | TT
T | TT | TT
Or
_ | T | t
T | TT | Tt
t | Tt | tt
In the first example, both your parents are tall, and all of their children will be tall. In the second example both parents are tall, both parents are tall, but there’s a 1 in 4 chance that their child will inherit the t gene from each of them and be short.
And not all genes are purely dominant/recessive, some are incompletely dominant, so Tt might sort of split the difference in height between a TT and a tt person. Some genes kind of play off of other genes, so maybe in order for the “T” gene to make you tall you may also need to be carrying a “U” gene, for example.
And on top of that, there’s environmental factors, nutrition, illness, injuries, etc. can have an impact on how tall you can be. People today are, on average, taller than people in the past because overall we’re better able to meet our nutritional needs and treat health issues than they were back then.
And, while it’s unlikely that you’ll grow another foot to catch up with your dad’s height, at 18 you may still have a little bit of growing to do, some men continue to grow a little into their early 20s.
So there’s a lot that goes into this.
Slovene@feddit.nl 1 day ago
How tall is the postman?