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    Monohybrid genetic cross to determine dominant trait

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    This is the genetic problem that I need to understand how to complete.

    Sand lizards in white sands new mexico:
    If for each species a lizard that was homozygous for the dark Mc1r allele had been crossed with a lizard that was homozygous for the light Mc1r allele the resulting F1 generation would have obtained the percentage of light skinned offspring shown below in coloum 2. If they had gone on to cross 2 offspring from the F1 generation, the resulting F2 generation would have obtained the results shown in column 3 below.
    for each of the 2 species state whether the light allele is dominant or recessive to the dark Mc1r allele. Draw mating diagrams to support your answer.It needs to show the crosses and the genotype and phenotype ratios that result in the F1 anf F2 generations.

    Lizard species % of light skinned lizards % of lizards in F2
    in F1 generation generation
    Sceloporus undulatus 100% 75%

    Aspidoscelis inornata 0% 25%

    Thanks in advance for any help you can offer. Bit confused on how to lay out the diagrams.

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    Solution Preview

    This cross represents a basic monohybrid cross. You are examining one trait, lizard color in this mating. In order to determine which characteristic, light or dark, is dominant you must first understand the terms dominant and recessive. Each organism contains two copies of every gene, usually refered to as alleles of that gene (one copy came from the mother, one from the father). These two alleles interact to determine what the organisms phenotype will be (what they will look like). The lizards that began the cross (the parental generation) were both said to be homozygous. This means that their two alleles are identical. The light colored lizard will have two light alleles while the dark colored lizard will have two dark alleles. When these lizards are crossed the light lizard will give a light colored allele to the offspring and the dark lizard will give a dark colored allele to the offspring. The resulting F1 generation is then said to be heterozygous, their two alleles are not the same. By examining what color these F1 lizards are you can determine which trait is dominant. When there are two different alleles in the genotype the one that overpowers the other and is seen in the phenotype is considered the dominant trait. So if all the F1 lizards are light then the light allele is the dominant one, if they are all dark than the dark ...

    Solution Summary

    This provides a detailed explanation of how to complete a basic monohybrid genetic cross. It diagrams how you would draw a punett square to examine the offspring of two different colored animals. You will also learn difference between dominant and recessive alleles and how you can determine which trait is dominant and which is recessive based on the offspring of a specific genetic mating. This explanation provides both written text and the diagrammed punnet square to help with your understanding.