Question

Why Mendel cross- fertilized the first parent plant while self- pollinated the second parental plant?

Answer 1

Dear student,

Gregor Johann Mendel (1822 – 1884) was the first to carryout the study on the transmission of characteristics from the parents to the offsprings. He proposed that heredity is controlled by factors, which are now believed to be segments of chromosomes or genes. Mendel performed experiments on a garden pea (Pisum sativum) with different visible contrasting characters. He proved the following points through which he proposes the three laws of Inheritance.

• True breeding pea lines were obtained by continuous self pollination for several generations.
• Fourteen true breeding pea lines were selected as pairs, which were similar except for one character with contrasting traits.
• Artificial cross pollination (hybridisation) was performed on such varieties to obtain first hybrid generation known as the first filial progeny or F1 .
• After hybridisation, the F1 generation so obtained resembled only one of its parents (say, all tall; no dwarf).
• When two plants from F1 generation were self pollinated, the second filial progeny or F2 generation was obtained.
• Revival of unexpressed trait (dwarf) was observed in some F2 progeny. Both traits, tall and dwarf, were expressed in F2 in ratio 3:1.
• Mendel proposed that something is being passed unchanged from generation to generation. He called these things as ‘factors’ (presently called genes).
• Factors contain and carry hereditary information.
• Alleles − Slightly different form of same factor.