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Leopard Gecko Genetics

Leopard Geckos morph, patterns or colouration are controlled by three main factors, Genes, Selective Breeding and incubation temperature. As an introduction to genetics I have created a table below which will attempt to identify what method is used to produce some of todays available morphs.

Leopard Gecko Morphs & Gentics
Morph	Genetic	Selective Bred	Temp. effects	CO-DOM	Notes
Normal	O	O	O	O
Albino	X	O	O	O
Banana Blizzard	X	O	O	O	Patternless and Blizzard
Blazing Blizzard	X	O	O	O	Albino and Blizzard
Blazing Banana Blizzard	X	O	O	O	Albino + Blizzard + Patternless
Blizzard	X	O	O	O
Circle Back	X	O	O	O
Giant	X	0	O	O
High Yellow	O	X	O	O
Hypo	O	X	O	O
Jungle	X	O	O	O
Lavender	O	X	X	O	Incubate @ 84-86F
Mack Snow	X	0	O	X
Melanistic	O	X	O	O
Pastel	X	O	O	O
Patternless	X	O	O	O
Patternless Albino	X	O	O	O	Patternless + Albino
Reverse stripe	X	X	O	O	Jungle Gene + Selective Stripe
Snow	O	X	O	O
Stripe	X	X	O	O	Jungle Gene + Selective Stripe
Super Mack Snow	X	0	O	X
Tangerine	O	X	O	O
Tangerine Albino	X	X	O	O	Albino Gene + Selective Tangerine

Although all of the morphs in the above table can be improved by modifying the incubation temperature I have only identified one in the list, as this is of special note. As a general rule the higher the incubation temp. the lighter and brighter the colours, the lower temps are used to darken hatchling colours and are used for chocolate Albinos and Melanistic morphs.

Genetic terms and words

Within the study of genetics and leopard gecko breeding several words and terms are used to describe the genetic properties of a hatchling, it is important to understand these phrases so I have listed some below with brief explanations.

Het or Heterozygous: This means that the hatchling is carrying the gene for a specific trait but only one gene out of a pair is of the special trait. For example hatchlings could have a gene for Albino, Blizzard or Patternless but would not express the trait outwardly as only one half of a set of paired genes has the mutation.

Homozygous: This is the opposite of Heterozygous (Het) and means the the hatchling is carrying two copies of a specific gene one each from it's parents. This would cause the hatchling to express the given trait in its Phenotype.

Phenotype: Is used to describe the way a hatchling looks, for example if the hatchling is a Blizzard, Patternless or an Albino, where its genetic makeup can be visibly detailed this is the Phenotype of the hatchling.

Genotype: Is used to describe the genetic make up of a hatchling whether it be seen or not, so a Blizzard Het Albino would be its Genotype, its Phenotype would be Blizzard as this is the only visible genetic trait that is outwardly displayed.

Recessive Trait: Refers to traits that are not expressed when combined with a dominant trait. All Albino, Blizzard and Patternless traits are recessive in Leopard Geckos.

Line Bred Traits: This refers to traits that were produced through selective breeding. Breeders selected the best examples of these traits in their collections and bred them together. Traits such as Tangerine, Hypo and Carrot Tail are all line-bred traits. These traits are not controlled by a pair of genes, but a selection of increase / decrease alleles. For example if you had a great specimen of a Leopard Gecko who had a 90% carrot tail and you bred it to a normal phase Leopard Gecko. What you would get is a diverse range of hatchlings showing varying amounts of Carrot Tail, some may even show no Carrot colour at all!

Genetic gene probablity calculations

		Male
		a	a
F e m a l e
	A	Aa	Aa
	A	Aa	Aa

Albino Example: Now that we have described some of the concepts of genetics lets try and put some of them in to practice to determine what genotypes and phenotypes can me made from albino parents. When determining what genes will be past on to a pairs offspring it is sometimes easier to define it in a chart. The chart to the right shows the results of pairing a Male Albino to a Normal female, all the offspring will be het albinos. You will notice the dominant (normal) gene is always represented by an uppercase letter and the mutated gene as a lowercase letter.

		Male
		a	a
F e m a l e
	A	Aa	Aa
	a	aa	aa

Albino Example 2: Now lets examine a grid where we breed an Albino Male to a Het Albino female. The blue letters represent the genes for albino that can be passed on by the Male, the pink letters represent the genes that could be passed on by the Female. From the diagram you can see that 50% of the offspring will have a phenotype of Albino (the ones with a pair of albino genes) and 50% will be het for albino, the offspring containing only one copy of the albino gene.

		Male
		A	a
F e m a l e
	A	AA	Aa
	a	Aa	aa

Albino Example 3: The last Albino example shows a commonly asked for result, the breeding of two hets. The results of this breading are as follows 25% of the hatchlings will be Albino, 25% will be normal, and 50% will be Het for Albino.

		Male
		PA	pA	Pa	pa
F e m a l e
	PA	PPAA	PpAA	PPAa	PpAa
	pA	pPAA	ppAA	pPAa	ppAa
	Pa	PPaA	PpaA	PPaa	Ppaa
	pa	pPaA	ppaA	pPaa	ppaa

Double Het Example : Lets say we have a pair of leos which are both het for Patternless & Albino. We breed these two together and get the table which is to the right. It looks confusing as there is a lot going on so I will colour code the result for ease of viewing. Out of this double het pairing only 1 hatchling in 16 will show both traits ie have a phenotype of Patternless Albino, which is marked in red. Anything that has a phenotype of Albino is shown in green and anything having a phenotype of Patternless is shown in white. The black results have a phenotype of Normal. Below I have listed both the Phenotype and Genotype results of the pairings in a table format.

Results of double het breeding 16 possible combinations
Genotype	Phenotype
1 without traits	9 No Traits
2 Heterozygous for Albino	3 Showing Albino
2 Heterozygous for Patternless	3 Showing Patternless
1 Homozygous for Albino	1 Showing Patternless Albino
4 double hets
1 Homozygous for Patternless
2 Homozygous for Albino Heterozygous for Patternless
2 Homozygous for Patternless Heterozygous for Albino
1 Homozygous for Patternless & Albino

Triple Het Example : Lets say we have a pair of leos which are both het for Patternless, Albino & Blizzard. We are attempting to create some Banana Blazing Blizzards from triple hets, a long shot I know. The results are shown in the two tables below. Red denotes a Banana Blazing Blizzard hatchling, as you can see there is a 1 in 64 chance of hatching one. Patternless Albinos are shown in white, Blazing Blizzards in green & Banana Blizzards in yellow.

		Male
		PAB	PAb	PaB	Pab	pAB	pAb	paB	pab
F e m a l e
	PAB	PPAABB	PPAABb	PPAaBB	PPAaBb	PpAABB	PpAABb	PpAaBB	PpAaBb
	PAb	PPAAbB	PPAAbb	PPAabB	PPAabb	PpAAbB	PpAAbb	PpAabB	PpAabb
	PaB	PPaABB	PPaABb	PPaaBB	PPaaBb	PpaABB	PpaABb	PpaaBB	PpaaBb
	Pab	PPaAbB	PPaAbb	PPaabB	PPaabb	PpaAbB	PpaAbb	PpaabB	Ppaabb
	pAB	pPAABB	pPAABb	pPAaBB	pPAaBb	ppAABB	ppAABb	ppAaBB	ppAaBb
	pAb	pPAAbB	pPAAbb	pPAabb	pPAAbB	ppAAbB	ppAAbb	ppAabB	ppAabb
	paB	pPaABB	pPaABb	pPaaBB	pPaaBb	ppaABB	ppaABb	ppaaBB	ppaaBb
	pab	pPaAbB	pPaAbb	pPaabB	pPaabb	ppaAbB	ppaAbb	ppaabB	ppaabb

Results of tripple het breeding 64 possible combinations
Genotype	Phenotype
7 Normals Het for Patternless, Albino & Blizzard	27 Normals
4 Normals Het Patternless & Blizzard	9 Patternless
4 Normals Het Albino & Blizzard	9 Albinos
4 Normals Het Albino & Patternless	9 Blizzards
2 Normals Het Patternless	3 Banana Blizzards
2 Normals Het Albino	3 Patternless Albinos
2 Normals Het Blizzard	3 Blazing Blizzards
1 Normal Het Patty & Blizzard	1 Blazing Banana Blizzard
1 Normal
4 Albino Het Patternless & Blizzard
2 Albino Het Blizzard
2 Albino Het Patternless
1 Albino
4 Blizzard Het Patternless & Albino
2 Blizzard Het Patternless
2 Blizzard Het Albino
1 Blizzard
4 Patternless Het Albino & Blizzard
2 Patternless Het Albino
2 Patternless Het Blizzard
1 Patternless
2 Patternless Blizzard Het Albino (Banana Blizzard)
1 Patternless Blizzard (Banana Blizzard)
2 Patternless Albino Het Blizzard
1 Patternless Albino
2 Blizzard Albino Het Patternless (Blazing Blizzard)
1 Blizzard Albino (Blazing Blizzard)
1 Albino Blizzard Patternless (Blazing Banana Blizzard)

Creating a multi gene morph:

If we want to create a multi gene morph from scratch we have several options depending on what animals we have to start with. Lets say we would like to produce a Leopard Gecko with a Phenotype of Patternless Albino. Below in the table I have listed some of the starting points a breeder may be starting from.

Multi Het starting points
Starting Point 1	Starting Point 2	Starting Point 3
Male Albino. Female Patternless.	Male Albino. Female 1 Patternless. Female 2 Patternless.	Male Albino Het. Patternless Female Patternless Albino
NOTE: Starting point 1 method means you have to breed siblings together this may result in an increased chance of defects in the hatchlings produced.

It is possible to start with a breeding pair which is only het for a trait but this relies on a lot of luck and it could take a breeder years to produce a Patternless Albino. In year one the breeder would breed together the pair of Hets incubate half of the eggs for male and the other half for female. Only one in four of the offspring will carry (be heterozygous for) both of the required genes. So if the breeding pair produce 8 eggs, 4 incubated for Male and 4 incubated for female, if luck is on the breeders side then 1 of the Males and 1 of the females are carrying both the requred genes. On year two the breeder would have to select breeding pairs and examine the results of year two's breeding. The breeder could expect a couple of albino and patternless or if luck is with the breeder a Patternless Albino. The breeding pairs on subsequent years would have to be shuffled around to identify which traits the breeding pairs carry or until a pair produce a Patternless Albino. The original pair from year one would also be bred each year to produce more suspected hets. This method is long and tedius and unlikely to produce reasonable results, although the breeder may be able to jump to starting point 1 on year two and produce a patternless albino on year three.

I have chosen 3 viable starting points for a breeding project..

		Male
		a	a
F e m a l e
	p	pa	pa
	P	pa	pa

		Male
		PA	pA	Pa	pa
F e m a l e
	PA	PPAA	PpAA	PPAa	PpAa
	pA	pPAA	ppAA	pPAa	ppAa
	Pa	PPaA	PpaA	PPaa	Ppaa
	pa	pPaA	ppaA	pPaa	ppaa

Starting point 1 is the one of longest methods to use as you can not produce any Patternless Albinos in year one. The advantage of starting with a homozygous pair is that you know the Genotype of every hatchling. In this example all hatchlings will be Het. Patternless Het. Albino. On year one the breeder will introduce the Homozygous pair for mating then incubate 2 eggs for male and the rest for female.

On year two half of the double het. females are bred to one double het. male, the remaining double het. females are bred to the remaining double het. male. This will give the results shown to the right. As you can see there is a 1 in 16 chance of producing a Patternless Albino.

To Be Continued...