Genetics Info & Tutorial: Something-zygous

A supplement to the 2008 Cornsnake Morph Guide

There are a few more terms that are commonly used when discussing genetics: heterozygous and homozygous.

A fertilized egg is called a zygote. The word zygote is part of the terms heterozygous and homozygous. These terms describe the relationship of a pair of corresponding genes. Hetero- means “different” --as in “heterosexual”-- and homo- means “same” --as in homosexual. So naturally, a homozygous animal has two copies of the same gene, whereas a heterozygous animal has two different copies of genes for the same trait (at the same locus)

Since heterozygous is often used in discussions and is a long word, it is abbreviated to “het.”


		A snake with both normal copies can produce melanin and will look normal. Since both copies are the same, this animal is called “homozygous normal.” But since the normal gene is already expected, it is unnecessary to specify this, so it is shortened to “normal” or “wild-type.”

	A snake with one normal copy and one mutated copy can produce melanin and will look normal. Since both copies are different, this animal is called “heterozygous for amel.” Technically, this animal is actually “heterozygous for normal and amel.” But again, it is pointless to specify that the other gene is the wild type since the normal gene is already expected to be there. This could also be called a carrier for amelanism, since it is carrying--but not showing--the mutant gene.

	A snake with both mutated copies cannot produce melanin and will look amelanistic. This snake could be called “Homozygous for amelanism.” But there is no point in specifying that it is homozygous--if it were not homozygous, it wouldn’t lack melanin--so just plain “amelanistic” is all that’s necessary to describe its genes.

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