Mendelian laws of inheritance

 Mendelian laws of inheritance
Mendel’s first law: The Law of Segregation

Mendel’s law of segregation explains what occurs at the alleles that constitute a gene during formation of gametes. For instance, suppose that a pea plant is composed of a gene for flower color in which the two alleles code for red.

View also Jean lamarck’s theory of evolution
One way to symbolize that condition is to write RR, which indicates that both alleles (R and R) code for the color red. An additional gene might possess a diverse combination of alleles, as in Rr.

In this situation, the symbol R stands for red color and the r for “not red” or, in this situation, white. Mendel’s law of segregation says that the alleles that constitute “a gene” break up from each other, or segregate, during the formation of gametes.

That law can be represented by simple equations, like:

RR → R + R or Rr → R + r

Mendel’s second Law: Law of independent assortment

Mendel’s second law-the law of independent assortment refers to the fact that any plant contains a lot of different kinds of genes. One gene determines the colour of the flower, a second gene determines length of stem, a third gene determines shape of pea pods, and so on.

Mendel observed that the manner in which alleles from dissimilar genes divide and then recombine is unconnected to other genes. That is, assuming that a plant contains genes for color (RR) and for shape of pod (TT).

Then Mendel’s second law says that the two genes will segregate independently, as shown below:

RR → R + R and TT → T + T

Mendel’s third law: Dominance

Mendel’s third law takes care of issue of dominance. Assuming that a gene is composed of an allele for red color (R) and an allele for white color (r).

What colour will the flower of the final plant take? Mendel found out that in every pair of alleles, one is more likely to be expressed than the other.

In other words, one allele is dominant and the other allele is recessive.

In the example of an Rr gene, the flowers produced will be red for the fact that the allele R is dominant over the allele r.


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