Question

discuss mendels law of inheritance

Answer 1

Inheritance is the acquiring of genetic characteristics or traits from parents by their offspring. In humans, both parents equally contribute to the inheritance of traits. In 1860, Gregor Mendel studied the rules of inheritance of traits. He conducted an experiment on pea plants for the same. He cultivated pea plants and observed their pattern of inheritance from one generation to next generation. This observation resulted in the discovery of three laws of inheritance, famously known as Mendel’s laws of Inheritance. Let us have a brief discussion on the contribution of Mendel in establishing the law of inheritance of traits.

Mendel’s Contribution to the Inheritance Law

Mendel is known as the father of genetics. Mendel’s laws are Law of Dominance, Law of Segregation and Law of Independent Assortment. These laws come into existence by experiments on pea plants with a variety of traits.

In the first experiment, only single character (plant height) was considered and was known as monohybrid inheritance. Another experiment was based on two characters (seed shape and color), thus called dihybrid inheritance.

Monohybrid Inheritance:

Here, Mendel crossed one tall and short pea plant and a tall plant was formed. He called this as first generation (F1) and offsprings were called F1 progeny. Again, he obtained the second generation by crossing F1 progeny with parent plants. This resulted in both tall and short plants in the ratio of 3:1. Mendel observed that traits which were absent in F1 generation had reappeared in F2 generation. He called such suppressed traits as recessive traits and expressed traits as dominant traits. These observations led to the formulation of Law of Segregation and Law of Dominance.

Dihybrid Inheritance:

Mendel took two contradicting traits together for crossing i.e. color and shape of seeds. He chose a round yellow seed and a wrinkled green seed and crossed them. He obtained only round yellow seeds in the F1 generation. Then, F1 progeny was self-pollinated which gave four different combinations of seeds i.e. round-yellow, wrinkled-yellow, round green and wrinkled green seeds in F2 generation. Thus he concluded that characters are distributed independently and inherited independently. Based on this observation he developed his third law- Law of Independent Assortment.

Later based on the conclusions and observation of Mendel relation between traits and inheritance, factors (genes) responsible for heredity were discovered.

Answer 2

According to Mendel's First Law of Inheritance or The Law of Dominance, ''In the cross between two parents who differ in one genetic characteristic for which they are both homozygous, all the offsprings in the first filial generation are equal to the examined characteristic in the genotype and phenotype showing the dominant trait...''

According to Mendel's Second Law of Inheritance or The Law of Segregation, ''The characteristics or the traits of an organism are determined by internal factors which occur in pairs. Only one of a pair of such factors can be present in a single gamete...''

According to Mendel's Third Law of Inheritance or The Law of Independent Assortment, ''In the inheritance of more than one pair of traits in a cross simultaneously, the factors responsible for each pair of traits are distributed independently to the gametes...''

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