Genetics 101. The short version

I hear you asking now "That's great Morti, but what's it all mean?" Here are a few definitions to get you started:

Gene: A sequence of chemicals in DNA or RNA that determine the transmission of certain traits to offspring.

Mutation: A subtle change in a gene that causes an inheritable trait to change.

Morph: A cool sounding word for a genetic variation.

Trait: An inheritable characteristic such as skin color or pattern.

Allele: (Pronounced A-leel) Either of the 2 paired genes (one from the mother and one from the father) that determine inherited characteristics. Alleles are usually represented as letters with a capital letter being dominant and a lowercase letter being recessive.

Homozygous: Fully showing a genetic trait. It has 2 identical Alleles for that trait

Heterozygous: 2 different Alleles for a trait. Abbreviated het.

Wild Type (also called Without trait): Showing no sign of a genetic trait. It has 2 identical alleles. Abbreviated WT.

Dominant trait: A type of trait in which the homozygous form and the heterozygous form look the same.

Co-Dominant trait: A type of trait in which the heterozygous form looks different from both the Homozygous and Wild Type:

Recessive trait: A type of trait in which the heterozygous form looks the same as the wild type.

Now that you know what the words mean, let's talk about how it all fits together. When you have an animal that shows a trait and you want the offspring to show that trait, wouldn't it be handy to know how to go about doing that? Well when you get done reading this and taking diligent notes (there will be a pop quiz later) then you too will be able to predict what will happen about genetics.

The first step is figuring out what kind of trait it is: Dominant, Co-dominant, or Recessive. There are two ways you can go about doing this. You could breed an animal that shows the trait with an animal that does not and then breed the children together and collect all you data. Then you would have to compare the percentages of the offspring that show the trait with the statistics that I am going to give you in a bit. This method requires years of hard work and meticulous record keeping. Or you can just do your homework and find out from the people who have already done this hard work for you what type of trait you are looking at. I recommend the latter.

At this step I want to apologize to all of you non-boa people out there. I love boas and so all my examples are going to be about boas. If you would like to see genetics for different animals such as Bearded Dragons, I have only this advise: Write your Own Sheet.

One of the easiest traits to play with here is albinism. In Boas, albino animals are missing the chemicals in their skin that produce black pigment. Albinism is a recessive trait so we know that if you breed an albino to a wild type boa, you are going to get 100% heterozygous offspring. How do we know this I hear you asking? Punnett Squares!

A Punnett Square is an easy way to show what alleles the offspring are going to have. To make an easy way to talk about albinos, let's assign the letter "a" to the trait. If we do that, we can show the types like this:

Homozygous: aa

Heterozygous: Aa

Wild Type: AA

The following are punnett squares showing all the possible combinations dealing with albino boas:

Normal (AA) X Normal (AA)

	A	A
A	AA	AA
A	AA	AA

100% of the offspring are normal.

Albino (aa) X Albino (aa)

	a	a
a	aa	aa
a	aa	aa

100% of the offspring are albino.

Het (Aa) X Het (Aa)

	A	a
A	AA	Aa
a	Aa	aa

25% of the offspring are normal

50% of the offspring are Het

25% of the offspring are Albino

(Since there is no way to tell the hets from the normals, until you can prove the genetics with breeding, it is said to be 66% chance het for albino)

Het (Aa) X Normal (AA)

	A	a
A	AA	Aa
A	AA	Aa

50% of the offspring are normal

50% of the offspring are Het

Albino (aa) X Normal (AA

	a	a
A	Aa	Aa
A	Aa	Aa

100% of the offspring are Het

Albino (aa) X Het (Aa)

	a	a
A	Aa	Aa
a	aa	aa

50% of the offspring are Het

50% of the offspring are albino

That's it when it comes to a single trait. But what about those designer boas like Snow Boas? That is the same Idea, but you have to have a bigger chart. This time you pair alleles up with corresponding alleles. For instance, with snows you are combining an Anerytheristic (nn) trait with an albino (aa) trait. So a snow is represented as aann. Punnett Square time!

Albino (aaNN) X Anerytheristic (AAnn)

(Remember a capital letter is the dominant trait. In this case that means that not having the mutation is dominant.)

	aN	aN	aN	aN
An	AaNn	AaNn	AaNn	AaNn
An	AaNn	AaNn	AaNn	AaNn
An	AaNn	AaNn	AaNn	AaNn
An	AaNn	AaNn	AaNn	AaNn

So 100% of the offspring are Double Het (both Het for Albino and Het for Anerytheristic)

Now let's look at what will happen if you breed double Hets together:

Double Het (AaNn) X Double Het (AaNn)

	AN	An	aN	an
AN	AANN	AANn	AaNN	AaNn
An	AANn	AAnn	AaNn	Aann
aN	AaNN	AaNn	aaNN	aaNn
an	AaNn	Aann	aaNn	aann

6.25% WT

12.5% Het. Anerytheristic

6.25% Homozygous Anerytheristic

12.5% Het. Albino

25% Het. Albino, Het. Anerytheristic

12.5% Het. Albino, Homozygous Anerytheristic

6.25% Homozygous Albino

12.5% Homozygous Albino, Het. Anerytheristic

6.25% Homozygous Albino, Homozygous Anerytheristic (Snow)

Sometime in the future I will cover co-dominant genetics. Stay tuned!

This care sheet is property of Morti. Please do not re-use without his express permission.

	Heterozygous Heterozygous - the animal carries the gene for a genetic trait but does not outwardly demonstrate the trait. Example: A boa that is het for albino looks normal but carries the albino gene. When it is bred to another het for albino boa or an albino boa, a percentage of the offspring will be albino.