How to Make Punnett Squares Representing Eye Color
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How to Make Punnett Squares Representing Eye Color

Punnett squares are used to determine the genetic and physical characteristics of an individual. The monohybrid cross is dealing with one type of gene and this type of cross has an outcome of four gametes produced. The dihybrid cross is dealing with more than one type of gene and it has an outcome of sixteen gametes.

Genetics is a study of characteristics of an individual. Genetics of an individual is traced back from their family history. An individual can be homozygous or heterozygous according to the genes they carry. When a person is homozygous that means they carry the dominant genes. While on the other hand, a heterozygous individual carries the recessive genes. In order to determine the probability of an individual carrying a certain trait, the concept of punnett square is used. The outcome of the offspring carrying a certain genetic makeup or certain physical makeup is diagramed using a punnett square.

            The punnett square has different types of diagrams. The monohybrid cross and the dihybrid cross are the two types of punnett square diagrams that are commonly used to represent the genetic makeup of individuals. The monohybrid cross is formed by obtaining the genotypes from the parents. The genotypes could include homozygous or heterozygous alleles. The parent alleles may include dominant traits or recessive traits and then those traits are crossed with each other. When the first cross of the genotypes from the parents takes places then that is considered the F1 generation; meaning the first generation. From the F1 generation we look at the possible gametes. Then from the possible gametes we can determine the phenotype and the genotype ratios of that particular cross. After the first generation the continuation to the second generation is based upon the first generation. Thus, the F2 generation cross is based off of the gametes outcome of the F1 generation. In similar way the phenotype and genotype ratios of F2 generation could be determine by the gametes produced in the generation. The other commonly used punnett square is the dihybrid cross. The dihybrid cross shows more than one gene being crossed; within the same punnett square. When the genes of the dihybrid cross then there are sixteen possible gametes; compared to the monohybrid cross which has four possible gametes.

            Making the punnett square diagram requires making a box that has a two by two grid. The F1 generation cross is based upon the parent cross. In situation where the parent genes are BB representing dark brown color eyes, Bg representing hazel color eyes and gg representing green color eyes. For the F1 generation we would cross BB x gg which will then give us with the outcome of all four gametes showing the Bg trait. From the F1 generation the physical makeup will show hazel color eyes for the offspring and the genetic makeup will show heterozygous traits. The F2 generation represents the cross between the gametes produced by the F1 generation.  The eye color situation represented all Bg in F1 generation, then we would cross Bg x Bg for F2 generation. The punnett square for the F2 generation will then represent one BB, two Bg and one gg ratio. Thus, such cross in the F2 generation represents the genotype of 1:2:1 ratio and also the phenotype ratio of 1:2:1.

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