[diatomdude]

In my internet experience, there are a lot of resources for learning colour genetics, but it's sometimes hard to find everything in one place. So, I'm putting together a general guide for the CS art community. c:

Disclaimer: This guide is intended solely as a reference for artistic works. While I am a biology major doing quite a bit of genetics, I don't know everything and I make mistakes. I’ve done my best to make this guide fairly accurate, but it is still extremely simplified. So don’t use this a reference for your science class (and if you do, it’s not my fault if you get it wrong).

I’'ll be trying my best to put this together in a timely manner and keep it updated, but I am quite busy, so if you find any neat new papers, please, send them my way!

Topics to Be Covered:
Each topic covered will have basic information, as well as some more in-depth stuff and sources for anyone interested.


The Basics

-Vocabulary
-What is Gene? Basic Inheritance
-Dominance
-Punnet Squares
Mammalian Colour Genetics

-The Basic Pigments & Genes
-Domestic Cat Colour Genetics
-Domestic Cattle Colour Genetics
-Domestic Dog Colour Genetics
-Domestic Horse Colour Genetics
-Domestic Mouse Colour Genetics
-Domestic Rat Colour Genetics
Avian Colour Genetics

-The Basic Pigments & Genes
-Domestic Chicken Colour Genetics
-Domestic Budgerigar Colour Genetics

Topics may not be completed in order.

[diatomdude]

Back to Main Page - Basic Inheritance

Chromosome: How DNA is organized inside of cells. Basically, a long string of DNA packed up really tight. Most animals have 2 copies of each chromosome, one from each parent.

Gene: A bit of DNA that controls a specific function, called a trait. For example, one gene might make hair black, and another gene might make eyes blue. Found on chromosomes.

Locus: Where the gene is found on the chromosome.

Allele: An allele is one of the different version of a gene, found at the same locus (area of the DNA). For example, in a gene that controls hair colour, you might have 3 different alleles: one allele that makes hair brown, one that makes it red, and one that makes it blonde.

Genotype: What alleles an animal has.

Phenotype: The visible traits of an animal, such as fur colour, eye colour, markings, fur length, etc.

Heterozygous/Heterozygote: Has two different alleles for one gene.

Homozygous/Homozygote: Has two copies of the same allele for one gene.

Dominant Allele: Only needs one copy to change the phenotype completely. Heterozygotes and homozygotes look the same.

Recessive Allele: Needs two copies of the allele to affect the phenotype. Only homozygotes show the colour, while heterozygotes are "hidden" by the dominant gene.

Incomplete Dominant Allele: Heterozygotes look different from homozygotes. One copy of the allele changes the phenotype a little bit, two copies of the allele changes the phenotype a lot.

X-Chromosome: The "female" chromosome in mammals. Most female mammals have 2 copies of this chromosome.

Y-Chromosome: The "male" chromosome in mammals. Most male mammals have 1 copy of this chromosome, and one copy of the X-chromosome. Most female mammals do not have a Y-chromosome.

Z-Chromosome: The "male" chromosome in birds. Most male birds have 2 copies of this chromosome.

W-Chromosome: The "female" chromosome in birds. Most female birds have one copy of this chromosome, and one copy of the Z-chromosome. Most male birds do not have a W-chromosome.

[diatomdude]

Vocab - Back to Main Page

DNA & Chromosomes
All living things have a “genetic code” made of DNA, which works a bit like an instruction manual – it tells the cells how to work, what stuff to make, and how to make it. What genes an animal has is its genotype. What an animal looks like on the outside is its phenotype. Most of an animal’s phenotype will depend on what its genotype is.

DNA is stored in chromosomes, which are very long strings of DNA coiled up very tightly. Genes are sections of this DNA in special places on these chromosomes. Usually, each chromosome has different genes. The area of the chromosome where a gene is found is called a locus.


This is a chromosome. The different colour bands all represent genes on the chromosome.


Most animals have two copies of every chromosome – one from mom, and one from dad. This means that most animals have two copies of every gene.



An animal gets one half of its chromosomes (and the genes on them) from each parent.


This doesn’t mean that both copies of the gene are the same, though. There are different versions of each gene, called alleles. These different versions might do different things – for example, in a gene that controls eye colour, one allele might make eyes brown, and one might make them blue.



The same gene can have different versions, called alleles, which change how that gene works. In this example, one allele of a gene makes eyes brown, and the other allele makes eyes blue. You can tell it is the same gene because it is in the same place on the chromosomes.


If both copies of the gene are different alleles, the animal is heterozygous for that gene. If both copies of the gene are the same allele, the animal is homozygous for that gene.



Homozygotes (like the two on the left) have two alleles that are the same. Heterozygotes (like the one on the right) have two different alleles.

[diatomdude]

Wip

[diatomdude]

wip

[diatomdude]

Back to Main Page - Basic Inheritance - Vocab

How Animals Make Colours

Light is a kind of energy, that exists on a spectrum. We see only part of it, usually from about violet/blue to red. When light hits a surface, part of this spectrum is absorbed, and some of it is reflected back, hitting our eyes and allowing us to see.

[insert image here]

When all colours are present, our eyes see it as "white". Usually though, when light hits an object, not all of its energy makes it back to our eyes - some of it is absorbed. When every colour is absorbed equally, you see the object as a shade of black or grey.

[iamge here]

When an object has a colour, it means that it is absorbing some parts of the colour spectrum, but not all of it - what you see is the light that is not absorbed, and is instead reflected back.

There are two basic ways that animals make colours - pigments, and structural colours.

Pigments
Pigments are molecules that reflect a certain colour of light, like a dye or a paint. Most animals have some kind of pigment. They can either make their own pigments, or steal them from other creatures (usually plants) through their diet.

Melanins
Melanins are the most common pigments in animals. Nearly every animal on earth makes melanins - even humans! They are responsible for all dark colours, like blacks and browns, and either all or most of the yellows and reds. Melanins are the only kinds of pigments that most animals can make by themselves, and are usually the only type of pigments that mammals have.

There are two basic kinds of melanin: eumelanin and phaemelanin. Eumelanin causes black to dark brown colours, while phaemelanin makes yellowish to reddish brown colours.

[image here]

Carotenoids
Carotenoids are another kind of pigment. Animals cannot make carotenoids - but plants can! Some animals are able to take carotenoids from the plants they eat (or from eating other animals that ate the plants), and put them into their scales, feathers or skin for their own use. This is really common in birds and invertebrates, but mammals don't do this.

Carotenoids are very bright colours - usually yellows, oranges, and reds. In some cases, they can be green or blue.

[image here]

Because carotenoids come from food, animals that use them can change colour if you change their diet. A good example of this is flamingos - they get their distinctive pink colour from the algae and tiny plankton they eat! If you feed them food that doesn't have carotenoids, they will turn white.

Structural Colours

Structural colours are made because of the physical shape of certain structures in the animals fur, feathers, scales or skin, which make light reflect, refract and/or scatter in strange ways - like the rainbows created by crystals, or on oil slicks.

Tyndall Blue

Tyndall Blue is a type of structural colour caused by tiny air pockets or particles. When light hits these tiny particles or air pockets, blue light is reflected back, while all other colours can pass through unaffected. When you pair this with a dark background to absorb the colours that aren't reflected, you get a bright blue colour.

[image here]

This is what gives a lot of blue birds, like the blue jay, their distinctive colour. It can also make green, if the animals puts a layer of yellow pigment over top of the structural blue. This is what happens in green budgies.

Irridescence

Iridescence is caused when light is reflected off of two different layers in a surface. As the light bounces around, some of it hits itself and cancels out parts of the spectrum. Because of this, the colour looks like it is changes as you move, and may even appear "rainbow" - like a thin layer of oil on water. In birds, this effect is made by having tiny air spaces in their feathers. Other animals, like beetles, do the same thing with minuscule grooves in their hard exoskeletons.

[image here]

Some examples of iridescence in birds are magpies and grackles. Insects like jewel beetles also use this to make colours.

[diatomdude]

Okay, all good to post now.

[♥Meeshi♥]

Marking. This is incredible!! I'm gonna learn a lot from this, thank you!

[Ms.Shine]

mark

[Delete account;]

This is a very clever idea, considering the fact that there are some younger users on this site that can learn from this!
Thanks for posting this!