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Help Me Out with Genetics.

Discussion in 'Questions and Answers' started by Mikie, Sep 24, 2012.

  1. Mikie

    Mikie Member

    Can someone make me a list of dominant and recessive traits in leopard geckos, bearded dragons, and corn snakes? And help explain how they work? and how to get some morphs? I know it's alot, but it'd be greatly appretiated!:)
  2. AjaMichelle

    AjaMichelle Elite Member

    Lists of morphs are located here for each species:
    Reptile Caresheets

    I would suggest investing in some books on genetics like this one:

    Genetics For Herpers: The Reptile and Amphibian Breeder's Guide to Genetics: Charles Pritzel: Books

    It's much more than could be summed up in a post. I can get you started though. :)

    Your phenotype is your observed morphology, while genotype determines your observed characteristics.

    There are two classes of traits into which you may classify genotype, and the combinations of alleles (forms of a gene) that code your phenotype: Mendelian (discrete) traits and continuous (quantitative, polygenic) traits.

    A Mendelian trait is one which is determined by an allele at a single locus. It is in this type of inheritance that you see what are referred to as dominant and recessive traits. Continuous traits can take any value along a continuum (gradient) and are often determined by multiple genes.

    So phenotype may be determined by discrete traits (one allele) as in Mendelian inheritance, or phenotype may be determined by alleles that combine for any given characteristic as in continuous inheritance.

    Mendelian Traits - Albinism

    To say that a trait is dominant in genetics is to describe a relationship between alleles (forms of a gene) at a locus (the location of a gene on a chromosome). A dominant allele masks the expression of a recessive allele when both reside at the same locus. This means that phenotype (observable characteristics) are determined by only the dominant allele, despite the presence of the recessive allele at the same locus.

    The simplest example of Mendelian (discrete) traits is where a gene occurs in only two allelic forms, those being dominant and recessive. We can designate these forms as D and r, respectively. Combination of these alleles yields three possible sequences (genotype combinations): DD, Dr, and rr. You can verify this by way of a punnet square.

    Homozygotes have identical alleles at a locus. Heterozygotes have varying alleles at a locus.

    DD is referred to as homozygous dominant--- the same dominant alleles at one locus
    Dr is referred to as heterozygous dominant--- different (varying alleles) at one locus
    rr is referred to as homozygous recessive--- the same recessive alleles at one locus

    Albinism is a Mendelian (discrete) trait, so phenotypic expression is determined by one set of alleles at a locus.

    If we consider a simplified example of albinism in ball pythons, we can conjecture that the normal black-brown pattern (morph) of BPs is dominant and call it "D." Albinism is recessive. We'll call this "r." There are individuals who carry both alleles at the color locus and have the genotype "Dr." However, because albinism is recessive, the allele for albinism is masked by the dominant allele for normal patterning and carriers exhibit a normal color and pattern. It is only when both alleles at the locus are recessive that we see expression of the albino allele.

    Genotype --- Phenotype

    DD --- Normal
    Dr --- Normal
    rr --- Albino

    Continuous Traits - Eye Color

    Continuous traits are more complicated as phenotype varies along a continuous gradient. Human eye color is not just brown or blue, and green, but can also be hazel. :)

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