Describe the brief life history of Mendel. State his cross with suitable example


Gregor Mendel (1822-84) was the first scientist who gave scientific study on genetics he entered a monastery in Brunn (Austria) where he carried on his scientific investigations on hybridization of plants. The results of his eight years breeding experiments were red before the Natural History Society of Brunn in 1865 and in the following years these were published in the transactions of that society but his work remained unnoticed until 1900 when three distinguished botanists Hygo De Vries in Holland, Tschermak in Austrua and Correns in Germany discovered its significance. Since then, Mendel’s work has formed the basis of the study of genetics. Mendel dies in 1884 before he could see his work accepted and appreciated.

Mendel’s experiment: Mendel selected for his work the common garden pea. In the pea he found a number of contrasting characters, flowers purple, red or while plants tall or dwarf and seed, yellow or green smooth or wrinkled. He concentrated his attention on only one pair of characters at a time and traced them carefully through many successive generations. In one series of experiments he selected tallness and dwarfness of plants.
The results he achieved in these experiments were the same in all cases. It did not matter whether he took the dwarf plant as the male and the tall plant as the female or vice versa.

MONOHYBRID CROSS

For monohybrid cross only one pair of contrasting characters is taken into consideration at a time. Mendel selected a pea plant, 2 meters in height and another 0.5 meter in height. He brought about artificial crossing between the two. The progeny that resulted from these crossing were all tall. This generation known as the first filial generation or F1 generation was inbred. Seeds were collected and soon next year. They gave rise to a mixed generation of talls and dwarfs (but no intermediate) in the ratio of 3:1 i.e.  Three fourths talls and one fourth dwarfs. This generation is known as the second filial generation of F2 generation. All dwarfs of F2 generation bred true producing dwarfs only in the third and subsequent generations. Seeds were collected separately from each F2 tall plant and sown separately. It was seen that one third of the talls bred true to type, while the other two thirds again split up in the same ratio of 3:1. The F2 ratio is therefore 1:2:1 one fourth pure talls, half mixed talls and one fourth pure white.

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