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Question :How do Mendel's experiments show that traits are inherited independently? |
Answer» Solution :When Mendel first CROSSED pure-bred PEA plants having round-yellow seeds with pure-bred pea plants having wrinkled green seeds, he found that only round-yellow seeds were produced in the first generation. No wrinkled green seeds were OBTAINED in the F generation. From this, it was concluded that round shape and yellow colour of the seeds were dominant traits over the wrinkled shape and green colour of the seeds. When the `F_1` generation pea plants having round yellow seeds were cross-bred by self-pollination, then four types of seeds having different combinations of shape and colour were obtained in second generation `(F_2)`. These were round yellow, round green, wrinkled yellow and wrinkled green seeds. Such a cross is known as dihybrid cross as two sets of corresponding characters are considered.  Thus, the RATIO of each PHENOTYPE (or appearance) of the seeds in the F, generation is 9:3: 3:1. Mendel observed that round yellow and wrinkled green, and two new combinations of characteristics had appeared in the generation. These were round green and wrinkled yellow. On the basis of this observation, Mendel concluded that though the two pairs of original characteristics (seed colour and shape) combine in the `F_1` generation, they get separated and behave independently in the subsequent generation. |
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