Basic Genetics

Genetic and Morphological Terms

 (developed by Ron Michelotti)

Albinism- a simple recessive mutation where the animal completely lacks melanin

Allele- (see gene)

Anerytherism- a simple recessive mutation where the animal lacks erythrin, or red pigment

Axanthism- a simple recessive mutation where the animal completely lacks yellow and red pigment

Codominant mutation- this mutation is expressed in varying degrees whenever the mutant allele appears in the genotype; it can be intensified if the  offspring receives the mutant alleles from both parents (homozygous condition)

Dihybrid cross- shows the possible genotype of offspring as the result of the pairing of two different genes

Dominant character- the individual need only receive one dominant allele from one parent to be expressed (unlike a simple recessive trait); uppercase letters are often used in writing the genotype

Double Het(erozygous)- the animal is heterozygous for two different traits

F1 (filial 1)- 1st generation from parental generation (usually an original pair from a particular bloodline or wild type) 

F2 (filial 2)- 2nd generation from parental generation; in herpetoculture, these offspring have been selectively bred and are often more desirable in color and/or pattern variations

Gamete-  a sex cell (e.g. egg or sperm) often written in genotypic form when doing genetic crosses

Gene- a specific location (locus) on one of the animal's chromosomes responsible for a particular function (or character in this case); they are made up of a pair of alleles, each coming from the parents of the individual

Genotype- the animal's genetic makeup

Ghost- hypomelanistic and anerytheristic snake

Heterozygous-  refers to a situation where the genotype of a particular gene is dissimilar (e.g. Aa); a heterozygous organism is often referred to as a carrier of a specified gene, which may or may not be expressed depending on the mutation (i.e. dominant, recessive, codominant)

Homozygous- refers to a situation where the genotype (or pair of alleles) of a particular gene locus is (are) identical (e.g. AA, aa)

Hypomelanistic- a codominant mutation (in boa constrictors) where the animal lacks varying degrees of melanin, or black pigment

Phenotype- refers to the character actually expressed

Salmon Snow- hypomelanistic, anerytheristic, and albino snake

Simple recessive mutaiton- a charater controlled by only one gene and is expressed when the offspring receives the mutant alleles from both parents; lowercase letters are often used in writing the genotype

Snow- anerytheristic and albino snake

Sunglow- hypomelanistic and albino snake

Triple Het(erozygous)- the animal is heterozygous for three different mutations

A Simple Monohybrid Cross using a Punnett Square

Question: What are the possible offspring as the result of the pairing of a male albino boa with a female boa heterozygous for albinism?

Genotype of male:       aa
Genotype of female:    Aa

Answer: Approximately 50% of the offspring will be albino (aa) and the other 50% heterozygous for albinism (Aa).  Please notice, the het for albinos are carriers because they have the albino gene from one of their parents.

Sample Dihybrid Crosses

KEY of Alleles

S- codominat allele for "salmon" hypomelanism
s- normal allele for melanin production

A- normal allele for melanin production
a- recessive allele for albinism

N- normal allele for erythrin production (red pigment)
n- recessive allele for anerytherism

How to get Salmon Sunglow Boas

How to get Super Salmon Sunglow Boas and Salmon Sunglows Boas

How to get Ghost Boas

How to get Super Ghosts

What to expect of actual litters?

This photo is a litter produced by Boaman Mike resulting from the pairing of a male Double Het for Ghost (SsNn) and female anerytheristic (ssnn).  Notice, there are 8 co-dominant ghosts, 7 anerys, 5 hets for anery, and no double hets for ghost.  Remember, Punnett squares only give you the probable outcomes (listed below) as a result of various pairings.

Triple Het Breeding

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