Mendels Laws of the Inheritance of Traits


 
 
Concept Explanation
 

Mendels Laws of the Inheritance of Traits

Gregor Johann Mendel (1822—84) was an Austrian monk and botanist. He is regarded as the father of genetics as some of the basic laws of inheritance were proposed by him. In 1857, Mendel began a series of experiments on the pea plant (Pisum sativum) to study the pattern of inheritance of various characters. He chose pea plants for three reasons.

  • Pea plants are self-pollinating.
  • They are easy to cultivate.
  • They have sharply defined characters.
  • Mendel chose to study seven different characters in pea plants.

    The seven character that were chosen by Mendal were Stem height,  Flower color, Flower position, Pod shape, Pod color, seed shape and seed colour.

  • All these forms have two contrasting forms for single character. For eg : For the trait of height , there are present two contrasting alleles :- Tallness and dwarfness.
  • In his experiment Mendal crossed plants to The generation that was produced by crossing these two was called the first filial generation (F1).
  • When F1 plants were crossed among themselves, the generation that was produced was called the second filial generation (F2).
  • The results of Mendel’s experiments showed the following:

  • Whenever two traits of a character were crossed, the (F1)  plants showed only one of the traits; the other trait never appeared. It did not matter whether the trait came from the pollen or the egg.
  • The trait that did not appear in (F1) reappeared in (F2), but in 1/4 of the total number of plants.
  • He explained that each genetic character was represented controlled by a pair of unit factors. These unit factors came to be known as alleles. These alleles are said to be the two variants of a single gene.
  • One of the alleles came from one parent and the other from the other parent.
  • The first-generation plants of Mendel’s experiment were all tall plants.
  •  The allele representing dwarfness was neither destroyed nor altered.
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