Reptile Genetics Part 2

... Introduction to the terms Triple Heterozygous, Hypomelanistic, Co Dominant

Triple Heterozygous:

... the animal is heterozygous for three different mutations ( AaRrHh ), eg: Amelanistic ( aa ) , Anerythristic ( rr ) & Hypomelanistic ( hh )

Hypomelanistic:

... The hypomelanistic gene reduces the amount of melanin or black pigment. Unlike the Amelanistic gene which eliminates all black pigment the Hypomelanistic gene reduces the black pigment, usually hypomelanistic snakes have shades of grey where the black would be. In colubrids the gene is a simple recessive, but a Co Dominant gene in Boas. Shortened on some Price Lists to Hypo. Hypomelanistic Boas are called Super Salmons when they have the paired Co Dominant gene and Salmon when they are visibly heterozygous. Hypomelanistic Boas have two line the Orange Tails & the Salmons.

So how do we go about producing a Triple Heterozygous animal, well the easiest way is to start with a Snow ( aarr ), which we already know is expressing two genes, the Amelanistic & the Anerythristic, and breed it to a third mutation in this case a Hypomelanistic ( hh ). So lets look at the possible gene ( genotype ) combinations that are available the snow can only pass on ( ar ), and the Hypomelanistic can only pass on Hh, so lets put them in the punnett and see what w might produce. In this example we will be using Cornsnakes. ( A simple recessive Hypomelanistic gene ) .

As we can see by their not being any paired genes, the Cornsnake hatchlings will be normal looking. They will all carry the Amelanistic, Anerythristic & Hypomelanistic gene making them Triple Heterozygous.

Snow Corn X Hypomelanistic Corn = 100% Triple Hets for Amelanistic, Anerythristic & Hypomelanistic ( Hahr )

Now lt's look at a mating between a Snow boa ( aarr ) and a Hypomelanistic Boa ( Hh' ). Notice in this example when we write the Hypomelanistic gene we add a ( ' ) to the lowercase h. This is because the Hypomelanistic gene in Boas is Co Dominant. The ( ' ) is known as a prime and tells us that it is Co Dominant.

Co Dominant:

... A Co Dominant gene is one that is able to have an effect on the animal in it's heterozygous state. In other words it needs only one lowercase letter to have an effect. Co Dominant = Visible Heterozygous. When we write a Co Dominant gene in a Punnett Square we follow the lowercase letter with a ( ' ) also known as a prime. When two lowercase Co Dominant genes are present it further has an effect on the animals appearance and these snakes are known as " Supers " ( h'h' )

This is an example of a cross between a " Super Salmon " Hypomelanistic boa ( h'h' ) and a Snow Boa ( aarr ). As we can see there is is a Co Dominant gene involved donated by the ( ' ) we therefore know that this will have an effect on the appearance of the hatchlings, they will not be normal looking, but will be visibly hypomelanistic, they will also be heterozygous for Amelanistic & Anerythristic.

Snow Boa X  Super Salmon Hypomelanistic ( Co Dominant ) Boa = 100% Salmon Boa het Amelanistic & Anerythristic.

Keeping with the Boas what would happen if we crossed back two of the Salmon Boas het Amelanistic & Anerythristic ( Hh'AaRr ). The combination of genes available are ( HAR ) ( HAr ) ( HaR ) ( Har ) ( h'AR ) ( h'Ar ) ( h'aR ) ( h'ar ). Remember each parent passes on half it's genes, hence three letters each in this combination.

Snow:

...  A double recessive mutation. the result of combining the Anerythristic & Amelanistic genes. Snakes are typically white with pinkish markings.

Salmon Boa:

... A Salmon Boa is a visibly heterozygous foe Hypomelanistic snake. The hypomelanistic gene in Boa is Co Dominant, meaning that it only needs a single copy of the gene to have an effect on the snake.