How do interactions between the two copies of a gene in a diploid individual (do

Question

How do interactions between the two copies of a gene in a diploid individual (dominance) determine the relationship between genotype and phenotype?

How can we use Mendel’s rules to predict the probability of transmission for different combinations of genes or phenotypes and to statistically test those predictions?

How can Mendel’s observations be extended to explain more complex patterns of inheritance?

How has the concept of Mendelianinheritance been integrated with observations from other fields to define the modern biological sciences?

Explanation / Answer

In a diploid organism, one allele is inherited from mother and other from the father. An individual could inherit a dominant or recessive allele or a combination of both. For example, If the dimple forming gene is D then dimple formation either occurs in a dominant condition i.e DD or heterozygous dominant condition Dd. Dimple formation would not occur in a recessive condition i.e dd. This example makes it clear that how genotypes interact to produce a particular phenotype in the next generation.

Mother x father

DD X dd

Thus in all the progenies dimple formation would occur but in the heterozygous condition.

Mendel also came up with a way to figure out whether an organism with a dominant phenotype (such as a yellow-seeded pea plant) was a heterozygote (Yy) or a homozygote (YY). This technique is called a test cross. In a test cross, the organism with the dominant phenotype is crossed with an organism that is homozygous recessive. The test cross is a conclusion from Mendel`s another law i.e the law of segregation. On the laws that Mendel formulated various ratios are fixed for example -In his monohybrid crosses, an idealized 3:1 ratio between dominant and recessive phenotypes resulted. In dihybrid crosses, however, he found a 9:3:3:1 ratio.

Codominance, epistasis, hypostasis, incomplete dominance are the modes of inheritance called as the non-Mendelian inheritance which can be concluded from Mendel`s original theory. For example, In codominance, neither phenotype is recessive. Instead, the heterozygous individual expresses both phenotypes. In incomplete dominance is a heterozygous genotype that creates an intermediate phenotype (a mixture). Similarly, Epistasis is the phenomenon where the effects of one gene are modified by one or several other genes, which are sometimes called modifier genes.

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