Boa Genetic Terms and Definitions

For the hobbyist, understanding genetics can be a very rewarding and exciting piece of knowledge.  It allows you to better understand and explain your snakes color, pattern, size and what is so special about those attributes.   For a breeder or someone wanting to turn their hobby into a small income, understanding genetics is essential.  At first it may seem confusing, but it is rather simple.

Let’s first start off with some terms commonly used in genetics.

DNA – deoxyribonucleic acid.  This is basically the genetic code of all creatures.  It is the highest level.

Chromosome – Each cell in all living organisms has a nucleus or center of the cell. The Chromosome is a threadlike part in the cell nucleus that carries the genes in a linear order

Gene – A hereditary unit consisting of a sequence of DNA that occupies a specific location on a chromosome and determines a particular characteristic in an organism. Genes undergo mutation when their DNA sequence changes.  Genes are transmitted in the sperm and egg cells of the parents

Allele – one of two alternate forms of a gene that can have the same locus (position) on homologous chromosomes and are responsible for alternative traits; "some alleles are dominant over others"

Locus (plural = loci) – the location on a chromosome where a specific gene resides.  Think of it as an address.

Genotype – The genetic makeup, as distinguished from the physical appearance, of an organism or a group of organisms.  Note that the genetic makeup (construction) can differ from the physical appearance as some genes may be recessive.

Phenotype – The observable physical characteristics of an organism, as determined by both genetic makeup and environmental influences.

Heterozygous – Having different alleles at one or more corresponding chromosomal loci.  What this means in practical terms is that the animal possesses the genes for a genetic trait (Albinism) but does not physically exhibit that trait.  It is commonly abbreviated as HET

Homozygous – having two identical alleles at a given locus. This basically means that the animal possess the genes for a specific trait and displays the trait – for example an albino snake

Wild type – The phenotype most commonly seen in wild caught individuals.  Also commonly referred to as Normal.

Recessive – a mutant allele that changes the phenotype only when in the homozygous.  When heterozygous, the individual looks normal. Albino snakes are a good example here.  A snake will appear as an albino only when it is Homozygous (homo) for albino.  If it is HET albino, it has the albinism gene but does not display the characteristics of albinism

Co-dominant – a mutant allele that changes the phenotype when either homozygous or heterozygous.  If the genetic trait is co-dominant, both the homozygous and the heterozygous will display the genetic characteristic.  Pastel and Hypomelanistic are good examples here.  Statistically speaking, a co-dominant animal if bred to a normal animal (Salmon boa to a normal boa) would produce 50% salmon boas and 50% normal boas.

Dominant – a mutant allele that changes the phenotype when either homozygous or heterozygous.  A heterozygous individual looks like a homozygous individual. Super Salmon, Super Jungle are perfect examples. The key difference between dominant and co-dominant is if a Super Salmon boa is bred with a normal boa, 100% of the babies would be salmon.

Double Heterozygous – Double Heterozygous means the snake is a carrier for two different genetic traits, but does not display the genetic traits.  An example is a Sunglow x Normal.  The sunglow is a combination of albino boa and salmon boa.  When the sunglow is mated with a normal boa, some of the babies will be salmon Het Albino (since salmon is co-dominant) and the other babies will be double Het Sunglow (meaning they have both the traits of the sunglow boa but are not displaying those traits – they look like wild type or normal boas).

Triple Heterozygous – Just like the double Het above, but this means the snake is a carrier for three genetic traits.

F1 generation – first filial generation.  This is the first generation of offspring from the initial pairing of a pair of snakes.

F2 generation – second filial generation.  The offspring of two F1s.

Punnett Square – a tool for determining the possible outcomes of a given pairing between different snakes.  It is a grid used to show the genes of each parent and their possible offspring; a type of grid that can indicate all the possible outcomes of a genetic cross; also called checkerboard.  It was invented by Reginald Crundall Punnett, English geneticist

Hypomelanistic - Reduced levels of black pigment.  This is in essence the Salmon boa.

Albinism - Absence of black pigment.  The albino boas have red, yellow but NO black.

Anerythristic - Absence of RED pigment.  See the Anery boas for more info.

Ayanthic - Absence of Yellow