Reptile Genetics Terms

Aberrant- Deviating from the ordinary, normal, or expected (Bechtel, 1995).

Abundismus- A type of Melanism in which the specimen is not completely black, but shows a change in the elements of the basic pattern as consequence of the number of isolated black spots or dots in the nonblack areas of the pattern (Peters, 1964).

Adaptation, biological- Alteration of structure or function to suit a particular environment (Bechtel, 1995).

Albinism- The heritable condition observed as the inability to form melanin in the skin and scales (Allaby, 1991). Absence of pigment in animals usually pigmented; the state of having colorless chromatophores (Holmes, 1979). Lacking pigment and therefore appearing pink or white (Mattison, 1986). A genetic absence of tyrosinase (Bentley, 1982). The appearance created by a lack of black pigment in the dermal and epidermal chromatophores (Barker, 2006).

Albino- Normal pigment is absent from the scales (Allaby, 1985). The blood pigment hemoglobin is present and may result in pinkish specimens or specimens with red eyes (Mattison, 1991). A commonly used term for Amelanistic. (McEachern, 1991). An organism with absent or deficient melanin (Bechtel, 1995).

Albino = Having the absent or deficient melanin. Widely used term for "Amelanistic".

Allele = Either of the two paired genes which affect an inheritable trait.

Amelanistic = Having no melanin.

Anerythristic = Having no red color.

Axanthic = Having no yellow color.

Incomplete dominant = A gene that causes the homozygous form to look different than the wild-type and the heterozygous form to have traits of both. Some examples of this would be the Pastel, Woma Tiger, Yellow Belly, Mojave, Red Axanthic, Platinum, Butter, Cinnamon, Fire, Calico and Spot nose Ball Pythons.

Chromosome = Each cell in every living thing has a nucleus. Much of the nucleus is made up of a constant number of paired chromosomes. Each chromosome is a single, long strand of DNA in a protein matrix. The strand of DNA contains many genes.

DNA (Deoxyribonucleic Acid) = Molecules bearing genetic information of all living cells. Gene. Also referred to as “unit of inheritance.”

Dominant = A gene that causes an animal to look different than the wild-type and where the homozygous form and the heterozygous form look the same as each other. A simple example of this would be the Spider, Pinstripe and Granite Ball Pythons.

Double Heterozygous = being heterozygous for two different traits.

Triple Heterozygous = Heterozygous at three gene loci.

P generation = Two unlike individuals that begin a genetics experiment, or breeding program.

F1 generation = First filial generation; the offspring of the P generation. An F1 is a single member of the F1 generation.

F2 generation = Second filial generation; the offspring of two F1s.

F3 generation = Third filial generation; the offspring of two F2s.

Gene = Unit of heredity that determines the characteristics of the offspring.

Genetics = The study of heredity.

Genotype = An organism’s genetic composition. Heredity - the transmission of genetic characters from parents to offspring.

Het = An abbreviation for heterozygous.

Heterozygous = Possessing two different genes for a given trait. An animal with one mutated, recessive gene still appears normal; its mutated gene can be inherited by future offspring. A co-dominant animal is heterozygous for the dominant form of its mutated gene, yet is different in appearance than both the wild-type and homozygous forms.

Homozygous = A state in which both genes for a specific trait are the same. When a recessive gene is it its homozygous form, it makes the animal look different from the wild-type. When a dominant gene is in its homozygous state, it causes the animal to look different from both the wild-type and the heterozygous (co-dominant) forms.

Hypomelanistic = An animal having less black and/or brown color than a wild-type.

Leucistic = A pure white animal with dark eyes.

Locus = A gene’s position on a chromosome (plural: loci)

Melanin = Black or brown skin pigments.

Melanistic = Abnormally dark, especially due to an increase of melanin.

Mutation = An abnormal gene that under certain circumstances can cause an animal to be born with an appearance other than wild-type.

Normal = An animal with no mutated genes - "wild type" in appearance. (See wild type)

Phenotype = An animal’s external appearance, as caused by its genotype.

Possible Het = An animal from a known breeding that has either a 50% or 66% possibility of being "heterozygous" for a mutant gene.

A 66% possible het comes from breeding 2 heterozygous animals together: 50% of the offspring are heterozygous, 25% will be homozygous, and 25% will be wild-type. Of the normal appearing animals, 66% (or roughly 2 out of 3) will actually be heterozygous for the mutated gene.

A 50% possible het comes from breeding a heterozygous animal to a wild-type animal. All of the resulting offspring will be wild-type in appearance, but 50% of them will actually be heterozygous for the mutated gene and must be bred out to determine which animals are really hets.

Punnett Square = A learning tool for determining the possible outcomes of a given cross between individuals. It was developed by R.C. Punnett, an early British geneticist.

Recessive = A gene that affects an animal's appearance if it's present in the homozygous state. A heterozygous animal carrying a mutated, recessive gene looks normal. Some examples of this would be Albino, Ghost/Hypo, Caramel Albino, Axanthic, Piebald, Clown, Desert Ghost, Orange Ghost, Hypo, Genetic Stripe and Lavender Albino Ball Pythons.

Super = A Commonly used Herpetocultural term for the Dominant form of a Co-dominant mutation, I.E. Super Pastel.

Tyrosinase = An enzyme required for synthesizing melanin.

Tyrosinase-negative = An albino whose cells lack tyrosinase, producing a white and yellow/orange animal with pink eyes. A separate albino mutation from tyrosinase-positive. Also called T- .

Tyrosinase-positive = An albino not able to synthesize melanin, but capable of synthesizing tyrosinase, which results in lavender-brown skin color. Also referred to as T+.