In a monohybrid cross between tall pea plants (TT) and short pea plants (tt) a scientist obtained only tall pea plants (Tt) in the F, generation. However on selfing the F, generation peaplants, he obtained both tall and short plants in F, generation. Show the above observation with a diagram.
Show the above observation with a diagram.
On the basis of above observation with other angiosperms also, can the scientist arrive at a law? If yes, explain the law. If not give
justification for your answer.
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Answers
EXPLANATION
The scientist arrived at a law named Mendel's first law of inheritance: The characteristics of an organism are determined by internal 'factors' which occur in pairs. Only one pair of such factors can be present in a single gamete. The monohybrid crossing experiment that was done is explained as below
(i) Mendel crossed the tall plants with the dwarf plants and found that only the tall pea plants were produced in the first generation (F1). No dwarf plants were obtained in that generation. He concluded that the first generation showed the traits of only one of the parent plants that is tallness here. The traits of other parent do not show here.
(ii) He then crossed the tall plants of the first generation and found that tall plants and dwarf plants were obtained in the second generation in the ratio of 3:1. In other words in F2 generation, three fourth plants were tall and one fourth was dwarf.
(iii) Thus he concluded that the dwarfness was not lost but was merely suppressed in first generation that appeared again in the second generation. He called this repressed trait as 'recessive trait' and expressed the tallness trait as the 'dominant trait'.
(IV) Also it was observed that the traits in the first generation were either tall or dwarf but were not intermediate. In this way it was specified that the traits are inherited independently. The ratio 3:1 is known as the monohybrid ratio.
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