Reptile & Amphibian Forums

i know this is a stupid question but can someone tell me what het is short for.
thanks alot.

het is short for hetrozygous. It means that it only carries one gene for the trait. Homozygous would be where they carried two copies of the gene producing the trait.

Sean.

that they would show the trait.
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phflame
kingsnake.com host

Homozygous = a gene pair contains two copies of the same gene. These could be two copies of the normal version of the gene or two copies of a mutant gene.

Heterozygous = a gene pair contains one copy of one gene and one copy of a different gene. These could be a mutant gene and a normal version of the gene or two different mutant versions of the gene.

A heterozygous animal does not look normal if the mutant is dominant or codominant to the normal version of the gene. Example - a reticulated python with a tiger mutant gene paired with a normal gene is a tiger retic rather than a normal retic.

A heterozygous animal does not look normal if the the gene pair contains two different mutant versions of the gene. Example - a corn snake with a motley mutant gene paired with a striped mutant gene.

Corn snake mutant genes are recessive to their normal versions. A heterozygous corn snake with a recessive mutant gene paired with the normal version of the gene does look normal. And a corn snake with a two copies of a recessive mutant gene does show the mutant trait. But many people say that heterozygous corn snakes look normal and homozygous corn snakes show a given trait; this blanket statement is false.

Paul Hollander

I did believe that a homozygous animal always shows the trait. Can you specify which snake morph/color might be homozygous, but not show the trait?
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phflame
kingsnake.com host

>Can you specify which snake morph/color might be homozygous, but not show the trait?

Only gene pairs are homozygous. It is part of the definition. But I understand what you mean.

The following all derives from what the biochemists say -- that there is not a 1:1 correlation between the genes and what you see. It might help to think of the genes as stations in an assembly line and what you see as the assembly line's output. In other words, a block or diversion at one point in the assembly line can screw up the output without affecting the working of other stations in the assembly line.

A snake can be homozygous normal in the gene pair where the amelanistic mutant gene can occur and homozygous anerythristic at a different gene pair. Result -- the snake does not look normal; it is anerythristic.

Or the effect of one mutant gene can mask the effect of a different mutant gene. A snake that is both homozygous amelanistic and homozygous hypomelanistic does not have any melanin. As far as the amount of melanin goes, the snake does not show the effect of the hypomelanistic mutant gene pair, though there may be other subtle effects produced by the hypomelanistic mutant gene pair. This phenomenon is called epistasis.

Paul Hollander