gerbil genetics made pretty easy

Gene plans Meet Gene. He has the plans for every project.

Whether it's building a road or taking out the trash, Gene is on the job. He's in charge of gerbil hair colour, eye colour, tail length and everything else too. Gene jobs

* * * There's actually a whole lot of genes in all living things. Every gene is a piece of instruction for things to happen. And after those things happen, you get some sort of result. Maybe it's black hair all over a gerbil. Maybe it's red eyes. It could be anything. Remember that genes don't "do" anything directly. They just provide the instructions.

Genes come in pairs

Let's complicate things just a bit. Every gerbil has 2 sets of instructions for everything. One set comes from dad. We'll say it's Gene. The other set comes from mum. Let's call her Genevieve. Gene and Genevieve

But only one if them is really needed for each job. The other one mostly just sits there.

Why? Well, one set of instructions is usually enough to get the job done. Sometimes both sets of instructions, genes, get used. Each does part of the job. But let's not worry about that right now. We'll get back to it later.

Dominant and Recessive Genes

Let's jump ahead and assume Gene and Genevieve are humans at the moment. Humans, like other living beings, all have two genes for everything (one from each parent). And each parent can only send one of those two genes for each thing to their baby.

brown eyesSo Gene and Genevieve get married and have a baby. Each of them sends the baby one set of instructions, genes, for eye colour. If both sets of instructions are the same, it doesn't matter which one gets used. Either way, it comes out the same.

If Gene and Genevieve both send genes for brown eyes to the baby, the baby will have brown eyes. It doesn't matter if the colour comes from Gene or Genevieve. Baby will have brown eyes.

brown and blue eyesIf the 2 sets of instructions are different, it's not always possible for both things to happen at the same time. So just one set of instructions ends up being used. We call that gene dominant.

So if Gene sends instructions for brown eyes, and Genevieve sends instructions for blue eyes, what happens?

One of the sets of instructions isn't used. That one is called recessive. You might not even know it's there when you look at their baby's eyes. Brown eyes are dominant. Blue eyes are recessive. Baby will have brown eyes.

brown and blue eyesWhat if Gene and Genevieve both send instructions for blue eyes? Well, not much for it as the baby can't have anything but blue eyes! Recessive genes can only make recessive traits.

Enough about people.


Gerbils come in many colours. But did you know all the colours are made from just two different kinds of pigment?

Colour in mammals is made from stuff called "melanin." If there isn't any melanin, then it's white. The two kinds of melanin are "eumelanin" and "pheomelanin."

- - blacks, browns, grays
black slate dove

- - reds, oranges, yellows
argente argente cream ivory cream

No melanin
- - whites


A: Agouti

agouti agouti

Wild gerbils are all the same colour called agouti (or golden agouti). Agouti isn't one colour. It's several in a particular pattern. Agouti gerbils look mostly brown, but that's just part of it. The tips of their hairs are black. And if you push the hair back, you'll see it's dark gray closer to the skin. Not only that, if you look at the belly, the hair is white or cream. Eyes and nails are black.

So many colours in a fancy pattern! It was all created by natural selection without any help from humans.

Every once in a while a change happens by accident in a gene when gerbils breed. And something might change in the gerbil. In the wild, if the change is good, then in time there will be more gerbils with the new, slightly different gene. But if it doesn't make it easier for the wild gerbils to survive and have more pups, it'll often disappear. All gone.gerbil predators

Agouti is a darn good colour for wild gerbils. The patterns and shades make it easier for wild gerbils to escape from predators. The dark speckled back makes it hard for birds that eat gerbils to see them in the dry grass and rocks. The light belly makes them hard to see against the sky if a predator comes from underground to catch a gerbil.

painting gerbils blackThen humans started breeding gerbils. And one day there was a mistake in the agouti gene. But it was recessive and didn't make any difference to the way the gerbil looked. But humans bred closely related gerbils together. Soon enough 2 gerbils with the same mistake in the agouti gene were bred together. So what happened?

black gerbil pupWell, some of the pups were black. All over. All the places on the gerbil where the agouti gene makes browns and grays and whites were gone. There was nothing but black left. Well, almost. There was just a bit of stubborn white that stuck to chins and/or paws. Everything else was black.

How was Gene involved? Hard to say exactly. Turns out a whole section of the instructions for making agouti had vanished. Gone. It's a lot less work making black gerbils than agouti ones. All he had to do was paint the whole gerbil black. No fancy bits of brown or gray or creamy white.

ripped plansNow people wanted to write the gene information in short code, to make it easier to keep records. Here's how they did it:

A- or A* = agouti (not sure what the other gene is)
Aa = agouti (has a recessive gene for sure)
AA = agouti (know for sure no recessive gene)
aa = black (2 recessive genes)

Capital letters (like A) are always used for dominant genes. Lower case letters (like a) are always used for recessive genes.

Much of the time we're not completely sure if an agouti gerbil has a recessive gene for black. So we write A- or A*. The - and the * both mean we're not sure what the other gene is.

But a black gerbil can't have a dominant A. If it did, it would be agouti! So we know that black gerbils are always aa.alphabet soup

Phew! That was a lot of information! Don't worry. It gets easier now.

Alphabet soup

So that was A for agouti. B would be next. Except there's no b genes in gerbils. At least, not yet.

So then we have C. Small complication though. C and P affect each other. So we're going to do P first, then C. Yeah, I know. Alphabet soup.


P: Pink Eyes

Gene washerGene "bleaches" colours to lighten them. Bleached eyes

The natural colour for gerbil eyes, P, is black. pp is a pair of recessive genes that turn gerbil eyes red or pink. It's as if the eyes are bleached and the dark pigment is washed away. They end up looking reddish because blood is red, not white. They often appear a dark ruby red but can be lighter depending on the gerbil's colour.

pink eyes in flashUnless you look carefully, you might not notice your gerbil's eyes are red. But if you take a picture with flash, the light will reflect off the eyes and then they will look very bright indeed! You might consider using the red eye remover in your photo editing software. Avoid using flash if not necessary. Not shooting straight at the eyes helps too. Unless you like the bright red look! (Some people think Solar's bright eyes in this pic look freaky.)


pp strips out the black stuff that naturally protects the eyes from bright light and helps with good vision. Without it, more light enters the gerbil's eyes. Bright lights might even be uncomfortable for them. Their vision is not quite as good as gerbils with black eyes.

Occasionally they have to spend a bit of extra time trying to focus and have to move side to side to help them see how far away things are.

Not all pink-eyed gerbils do this. I rarely see it in ours. Some gerbils may do a more exaggerated version. It doesn't seem to affect their quality of life.

pp and coat colour

The other big effect of pp is a drastic lightening of the coat.

Watch what happens to a golden agouti gerbil when the eye colour changes from black to red; the black tips fade away and we get an argente golden gerbil. When the eyes on a black gerbil are made red by pp, the whole gerbil fades to gray, lilac.

golden agouti to argente golden black to lilac

A couple more examples. Nutmeg loses all the black in the coat to become red fox. A gray agouti without black becomes an ivory cream.

nutmeg to red fox gray agouti to ivory cream


NEXT PAGE: The C Locus (this one is fun!)

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