Trait: A physical manifestation that is distinguishable from the normal physical appearance.

Wild Type / Normal: The most frequently observed phenotype in the wild, or the one arbitrarily designated as "normal."

Sexual Dimorphism: Characteristic differences based on gender.

Aberrant Pattern: Deviating from the ordinary, normal, or expected. Typically refers to connected saddles or striping.

Mutant Gene: Any gene that is different from the corresponding normal gene. Not necessarily a visual mutation.

Dominant Mutant Gene: A mutant gene that has its trait expressed when the gene pair is either heterozygous or homozygous for the specific mutant gene. Heterozygous and homozygous specimens are not 100% distinguishable from each other. Note, with some dominant mutants, some of the specimens can be visually identified as heterozygous or homozygous.

Co-dominant Mutant Gene: Similar to "dominant mutant gene" except a homozygous specimen can be distinguished from a heterozygous specimen 100% of the time.

Recessive Mutant Gene: A mutant gene that has its trait expressed only when the gene pair is homozygous for the specific mutant gene. A heterozygous individual looks normal.

Heterozygous: (slang - het) The two genes in a gene pair are not the same. Most commonly the pair contains one normal and one mutant gene, but there could be two different mutant genes.

Homozygous: The two genes in a gene pair are the same. Can be two normal or two identical mutant genes.

Super: Slang term commonly used when a snake has a gene pair that is homozygous for either a dominant or a co-dominant mutant gene.

Double het: Has two gene pairs which are heterozygous. I.e., double het for snow would have a normal gene paired with an albino gene and a normal gene paired with an anerythristic gene.

Triple Het: Same as double Het except applies to three gene pairs.

Amelanistic / Albino:  An animal lacking melanin (black pigment).

Axanthic: The absence of yellow colour, or absent or deficient xanthophore pigment metabolism.

Hypomelanism: Having less than the normal amount of melanin. Hypomelanism can be caused by several unrelated mutant genes or by selective breeding.

Leucistic: An all white animal, except for some pigment in the eyes.

Melanin: Black or brown pigments synthesized from tyrosine.

Tyrosinase: The enzyme required to catalyse the first two chemical reactions in the synthesis of melanin.

Tyrosinase-Negative Albinism: Lack of melanin due to the inability to make functional tyrosinase. Kahl and Sharp albinos are known as tyrosinase negative albinos.

Tyrosinase-Positive Albinism: Lack of melanin in animals with fully functional tyrosinase. Melanin is not synthesized because of a defective enzyme other than tyrosinase. In boas, the term has been generalized to include production of less than the normal amount of melanin. This is caused by partly or completely defective enzymes produced by at least two unrelated mutant genes.

Albinism:  A genetic condition in which an individual does not produce the pigment melanin.

Allele: One of two or more possible alternative forms of a given gene. Alleles differ slightly in DNA sequence. The difference affects the functioning of the gene product (RNA and/or protein).

Back-Cross: A cross involving an offspring crossed with one of its parents i.e. A father x daughter or mother x son mating.

Base: A chemical subunit of DNA or RNA that encodes genetic information. In DNA, the bases are adenine (A), cytosine (C), guanine (G), and thymine (T). IN RNA, thymine is replaced by uracil (U).

Chromosome: One of the paired structures located inside the cell's nucleus that contains the genetic information of the cell.

Co-dominant: Two contrasting alleles that are both fully functional and both fully expressed when present. Two alleles produce functional biochemical products. The effect of both alleles can be detected. Heterozygous individuals have a phenotype that is often visually intermediate between the phenotypes of the two homozygous types.

Cross: The mating of parents to produce offspring during sexual reproduction.

Crossbreeding: Mating of differing individuals from the same species (interstrain), different species (interspecies), or different families (interfamily) to produce hybrids.

Deoxyribonucleic Acid {DNA}: The genetic material that serves as the instructions for the growth and development of most organisms. It is the chemical molecule that encodes genetic information in each living cell. Two linear molecules made of nucleotides entwine to form the DNA double helix.

Dihybrid: An organism that is heterozygous for both of two different genes.

Dihybrid Cross: A cross between parents that differ by two specified genes.

Diploid: A paired set of chromosomes, one derived from each parent, bearing two complete copies of nuclear genetic information for a cell.

Dizygous: Developed from two separate ova. Fraternal twins are dizygous because they develop from two separate fertilized ova.

Dominant: The controlling member of a pair of alleles that is expressed to the exclusion of the recessive member. An allele or trait that masks the expression of another allele or trait that is considered recessive to it.

Double Helix: A model of DNA structure proposed by molecular biologists James Watson and Francis Crick. The major features of this model are two strands of DNA wound around each other and connected by hydrogen bonds between complementary base pairs.

Enzyme: A special protein that controls metabolism by regulating chemical reactions in cells.

Epistasis: A genetic phenomenon in which a gene influences the expression of a second gene, usually by masking the effect of the second gene. However, only one trait is being controlled by these two genes, so epistasis is characterized by modified dihybrid ratios.

F1: First filial generation Offspring produced from a mating of P generation individuals.

F2: Second filial generation Offspring produced from a mating of F1 generation individuals.

Gamete: A reproductive cell: either egg (ovum) or a sperm (spermatozoan) containing half the genetic material of a normal cell.

Gene: A unit of heredity controlling a single trait; a segment of DNA that contains the instructions to build a protein with specific character-determining factors.

Genetics: An area of biology involving the scientific study of heredity.

Genetic Drift: Chance fluctuations in allele frequencies within a population resulting from random variation in the number of offspring produced by different individuals.

Genome: The total amount of DNA in an organism, emphasizing the collection of genes and other genetic information arranged linearly in chromosomes.

Genotype: The particular combination of genes, or the actual genetic makeup, for a particular trait found within an individual. The genotype is expressed as a set of symbols representing the alleles present.

Germ Cells: Reproductive cells such as eggs and sperm.

Haploid: A single set of chromosomes; mature gametes are haploid.

Heredity: The overall mechanism by which characteristics or traits are passed from one generation to the next. Genetics is the scientific study of heredity.

Homologous Pair: Two chromosomes that contain the same set of genetic loci. The genetic information contained on members of homologous pairs may be identical or consist of alleles.

Heterozygote: An individual with two different alleles for a gene. Often symbolized as Aa.

Heterozygous: A condition in which the two copies of a gene (one inherited from each parent) have different alleles. Often symbolized as Aa.

Homozygote: An individual with two like alleles for a gene. Often symbolized as AA.

Homozygous: A condition in which the two copies of a gene (one inherited from each parent) have the same alleles. Often symbolized as AA.

Hybridization: The exchange of genetic material between populations or species through mating between unlike forms.

Inbreeding: Mating between genetically related individuals.

Incomplete Dominance: A phenomenon involving two alleles, neither of which masks the expression of the other. Instead, the combination of the alleles in the heterozygous state produces a new phenotype that is usually intermediate to the phenotypes produced by either allele alone in the homozygous state. One allele produces a functional biochemical product, and the other allele produces a non-functional biochemical product. The effect of both alleles can be detected. Heterozygous individuals have a phenotype that is often visually intermediate between the phenotypes of the two homozygous types.

Inheritance: The genes that are received from one's parents; there are two genes for every trait, one contributed by each parent.

Locus: The specific location of a particular gene on a chromosome.

Lethal Allele: An allele capable of causing the death of an organism. A lethal allele can be recessive (two copies of the allele are required before death results) or dominant (one copy of the allele produces death).

Meiosis: The cellular reproduction process in which the chromosome number is reduced from two sets to one set, ultimately resulting in the formation of gametes (eggs and sperm).

Melanism: The opposite of albinism, a condition that leads to the overproduction of melanin.

Mitosis: The cellular reproduction process in which a cell duplicates it's internal contents and splits into two new cells; each new cell contains the exact chromosomal makeup of the original cell.

Monozygous: Developed from a single ovum (egg). Identical twins are monozygous because they originate from a single fertilized ovum that splits in two.

Multiple Alleles: A genetic phenomenon in which a particular gene exists in more then two alleles. The greater the number of alleles, the greater the genetic diversity.

Mutant: A trait or organism different from the normal or wild-type trait or organism seen commonly in nature.

Mutation: Any change in a DNA molecule that can be passed from one generation to another; usually leading to an altered phenotype.

Nucleic Acid: The genetic material of cells, found in two forms: Deoxyribonucleic Acid (DNA) and Ribonucleic Acid (RNA); composed of repeating subunits called nucleotides.

Nucleotide: The basic unit of DNA, consisting of a five-carbon sugar, a base containing nitrogen's, and a phosphate group.

P Generation: Parental generation, the original individuals mated in a genetic cross.

Parthenogenesis: The production of an organism from an unfertilized egg.

Phenotype: The observed physical or measurable manifestation of a trait. The outward appearance of an organism.

Protein: A macromolecule made of amino acids used for the function and structure of cells.

Pseudo Dominance: A genetic phenomenon involving a recessive allele on one chromosome that is automatically expressed because of the deletion of its corresponding dominant allele on the other chromosome of the homologous pair.

Punnett Square: Developed by English geneticist Reginald Punnett; this is the basic tool used by geneticists to determine the mathematical probability of a breeding producing offspring that will inherit a specific trait or traits.

Recessive: An allele or trait whose characteristics are not expressed unless it is paired with another recessive allele or trait.

Reciprocal Cross: A mating that is the reverse of another with respect to the sex of the organisms that possess certain traits. For example, if a particular cross were tall male X short female, then the reciprocal cross would be short male X tall female.

Ribonucleic Acid {RNA}: Another form of genetic material, usually a single-stranded substance consisting of units called ribonucleotides and used primarily for genetic expression through transcription and translation.

Sex Chromosomes: The X and Y chromosomes determine gender in an organism. These chromosomes are received from an individual's parents, each of whom contributes one sex chromosome to their offspring. A female carries two X chromosomes and a male carries one X and one Y chromosome.

Trait: A phenotypic characteristic that is inheritable

Transcription: The cellular process by which genetic information in the form of a gene in a DNA molecule is converted into the form of an mRNA molecule.

Translation: The cellular process by which genetic information in the form of an mRNA molecule is converted into the amino acid sequence of a protein, using ribosomes and RNA molecules as accessory molecules.

Wild Type: The normal genetic makeup of an organism. A trait that is common in nature. Alternatives to this trait are called mutants.

Zygote: A cell formed from the union of a male gamete (sperm) and a female gamete (ovum). Through successive cell divisions, the zygote will eventually give rise to the adult form of the organism.