Genetics explained

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Genetics explained

Post  Admin on Tue Dec 25, 2012 4:30 am

The mention of the word Genetics, is often enough to make anyone outside of the science community shudder. However for those of you that what to take your reptile passion to the next level and begin breeding you’ll find it very helpful to know some of basic mechanics behind genetics as well as the general terms used within this subject.The goal here is simply to introduce you to some of the basic element and how they apply to reptiles.

General Genetics

Gene: What causes traits/characteristics to be transferred or inherited to an organism’s offspring.
Genotype: Describes what an organism’s genetic composition is made up of.
Heredity: Passing of genetic characteristics from parents to offspring.
Phenotype: Describes what an organism’s external appearance looks like, which is a result of its underlying genotype.

Gene Terms
Mutation: An abnormal random gene that can cause an animal to be born with an appearance other than wild-type.
Dominant: Describes a gene that will produce the same appearance in the offspring – even if it is not paired to the same gene.
Recessive: Describes a gene that will only produce the same appearance if it is paired against the same gene.

For example if a reptile inherits a dominate gene for wild markings from one parent and a recessive gene for albino from the other parent – the dominate gene will be displayed in the reptile’s appearance and the albino gene will be masked. For the recessive gene of albino to be displayed by the reptile it must be inherited from both parents.
Het or Heterozygous: Describes an animal that carries two different genes for a given trait. The animal will display the dominant trait it carries but will also carry the genetics for the recessive gene.
Possible Het: Term used to describe an animal that has either a 50% or 66% possibility of being "heterozygous" for a gene
Homozygous: Describes an animal that carries the same gene for a specific trait. A recessive trait must be in its homozygous form for it to display the trait.
Co-Dominant: 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.
Super: A co-dominate mutation in its dominant form, essentially the super form of a co-dominant gene.
Some examples of supers would be the: super snow leopard gecko, super hypo boa and super pastel ball python. Any time that a super is bred to a normal wild type then all of the offspring will show the het homo form of the super. So in leopard geckos all snows will be produced, in boas all hypos will be produced and in balls all pastels will be produced. The super form in any way is a great addition to a breeding group as it opens up a whole new way to create new morphs when crossed with other genetically proven animals.

Appearance Descriptors
Albino or Ameleanistic: No, or minimal black or brown pigment
Anerythristic: No red pigment
Axanthic: No yellow pigment
Hypomelanistic: Displaying less black and/or brown pigment than a wild-type
Leucistic: Pure white with dark eyes
Melanin: Black or brown skin pigments
Melanistic: Abnormally dark due to an increase in melanin
Normal: No mutated genes and will display typical natural or wild appearance
Tyrosinase: Enzyme required for synthesizing melanin
Tyrosinase-negative or T-: Albino whose cells lack tyrosinase, display a white and yellow/orange appearance with pink eyes.
Tyrosinase-positive or T+: Albino not able to synthesize melanin, but capable of synthesizing tyrosinase, which results in lavender-brown skin color.
Xanthic: Displaying increased yellow.

So what does this all mean?
Genetics is all about how traits get passed down from one generation to the next. From the terms above you can see that it is not as simple as just looking at the traits a reptile may display because they also can carry underlying traits/genes that they will pass along to their offspring. A basic knowledge of how dominate and recessive genes work will take you a long way in understanding and developing selective breeding projects.
When two animals reproduce they “send” half of their DNA (genetic makeup) to their offspring. Every animal has two copies of each gene they carry, one inherited from the father and one from the mother. The best genetic tool for helping to understand how genes are passed along is the Punnet square. This square uses the genes each parent carries to calculate the combinations of genes for the offspring.
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