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Q. 11

Give reasons for the appearance of new combinations of characters in the F₂ progeny.

Class 10th NCERT - Science Exemplar 9. Heredity and Evolution

Answer :

In dihybrid cross, when pea plants with round and green seeds (RRyy) are crossed with plants with wrinkled and yellow seeds (rrYY), round and yellow colour (RrYy) seeds are produced in F1 generation. In F1 generation, the dominant alleles suppress the recessive ones. So, as a result only dominant allele are expressed. Thus, all the progenies in F1 generation, showed dominant traits only. However, genes for recessive traits were present in all the plants.

When F1 generation are crossed, they give rise to new combination in the F2 generation with round yellow, round green, wrinkled yellow and wrinkled green in the ratio 9:3:3:1.

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