Biology: How do dominant and recessive genes work?

Biology: How do dominant and recessive genes work?

You’ve got your mother’s eyes, your father’s mouth and your aunty’s tude. How does it happen?

It’s all in the genes

Let’s start with what these things actually are. An easy wayto describe genes is as a “blueprint” for your body, or a recipe for what makesyou into you.

A less easy way to describe them is as an informationsequence for building specific molecules such as hormones or proteins to growand maintain your body. They lurk inside your cells like little managers givingout orders: “Scatter some freckles there, curl up that hair over here. Morelength in these legs, more width on those ears.”

It’s not just external physical features, though. If you’relactose-intolerant, have sickle-cell anaemia or are in the AB blood group, that’sall down to your genes.

Dominant vs recessive

Sexually reproducing species have two copies of each gene.The two copies, called alleles, can be slightly different from eachother. The differences can cause variations in the protein that’s produced, orthey can change protein expression: when, where, and how much protein is made.Proteins affect traits, so variations in protein activity or expression canproduce different… stuff.

We call that “stuff” a phenotype, which it basicallya trait we can observe in a creature, like eye colour or a zebra’s stripepattern.

When a new living thing is created – a human, a cat, apiefor – there’s an internal war between options. Most of the time, dominantalleles win that battle, which is why you’ll often see the sons of championrugby league players also being pretty good at rugby league. But sometimes recessivealleles win, which is why you’ll occasionally see the sons of champion rugbyleague players preferring to write poetry instead.

But how does it work?

Like this:

Are you serious?

No, not really. But this bit is.

For each phenotype (you know, “piece of stuff”), you get oneallele from your mum and one from your dad. A dominant allele produces adominant phenotype in people with one copy of the allele (as in, from oneparent).

But! If we’re talking recessive alleles, you have to haveone from each parent to get that recessive phenotype. A good example in peopleis blue eyes – if both parents have blue eyes, their kids will as well.

On the other hand, if one parent has brown eyes (a dominant allele), their kids will have that recessive blue allele in their system somewhere, but are way more likely to have brown eyes. Of course, it gets more complicated as you move further along any given family tree…

What’s a piefor?

Eating with tomato sauce, silly.


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