CBSE Class 10 Science 2022 Delhi Term II Set 2

Question : 7

Total: 7

Mendel blended his knowledge of Science and mathematics to keep the count of the individuals exhibiting a particular trait in each generation. He observed a number of contrasting visible characters controlled in pea plants in a field. He conducted many experiments to arrive at the laws of inheritance.
(a) If only one pair of contrasting characters like tall and short plants is taken, plants obtained in F1 generation are not of medium height. Why?

Solution:

(a) This is because of the law of segregation. The plants will either be tall or short only. There is no mixing of alleles during crossing over in meiosis, hence, there is no allele to code for medium height. For homozygous condition (TT) all will be tall and for (tt) all will be short, and for heterozygous ( Tt ) all will be tall because of the law of dominance which states that only dominant allele expresses itself in heterozygous condition and the effect of recessive one is masked. Thus dominant character is expressed, i.e., tallness, out of the two forms of the character inherited.

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