Mendelism

 State the laws of Mendel. Why he selected pea plant for his experiment? What are the reasons behind Mendel’s success?

Reason behind the selection of pea plant: -

In the pea varieties available commercially, several characters had two contrasting forms, which were easily distinguishable from each other. This permitted an easy classification of F₂ and F₃ progeny from various crosses into clear-cut classes on the basis of contrasting from of the different characters.

Flower stricter of pea ensured self-pollination; this was experimentally verified by Mendel.

Pea flowers are relatively large, which facilitates emasculation and pollination.

Every year one generation of pea can be grown.

Pea seeds are large and present no problem in generation. Pea plants relatively easy to grow and each plant occupies only a small space.

 

In addition to pea, Mendel worked on Rajma (Phaseolus vulgaris L.) as well. The results from experiments on rajma were reported alongwith those on pea in the same paper.

Reason behind Mendel’s success: -

The most important factor that contributed to his success was his ability for an accurate and incisive analysis of the reasons for failure of earlier workers, and to avoid them in his work.

 At first, Mendel studied the inheritance of two and three character pairs.

Mendel selected pea varieties that had clearly different forms of one or more characters, i.e.,  contrasting characters. The different between contrasting characters was so large and clear-cut that the individuals of a population could be easily and accurately classified as having one or the other contrasting characters.

Mendel classified all the plants of a population on the basis of the contrasting characters under study, and kept an accurate record of the number of plants (or seeds) in each category for every generation.

Mendel carried out his experiment with great care and elaborateness. His carefulness avoided the confusing effects of various experimental errors on the findings.

His knowledge of mathematics was a definite assets for the interpretation of his findings. More notable was his clear understanding that ratios ranging from 2.82 : 1 to 3.51 : 1 were estimated of 3 : 1 ratio.

Mendel was able to formulate appropriate hypothesis on the basis of the explanation he offered for his experimental findings. Further, he proceeded to test these hypothesis experimentally to prove the correctness of his explanations.

      In spite of his brilliance in experimentations, analysis and interpretation, Mendel was undoubtedly lucky. Because 1) the seven characters selected by Mendel showed qualitative inheritance, and not a single one was inherited quantitatively. 2) The contrasting forms of each of the seven characters were governed by a single gene, and in each case one form was completely dominant over the other. 3) Of the seven characters studied by Mendel, the genes for two were located in one chromosome, while three others were present in another chromosome. But out of these, only two were close enough to distort the dihybrid ratio, and Mendel did not study this characters pair. Truly, ‘God helps those who help themselves’. But sooner or later, the luck of any person runs out. And luck did desert Mendel in his efforts to convince his contemporary biologists about the significance of his findings.