CBSE Class 10 Answered

Dear student,

Allele is either of a pair or series of alternative forms of a gene that can occupy the same locus on a particular chromosome and that control the same character. Some alleles are dominant over others.

The gene for seed shape in pea plants exists in two forms, one form or allele for round seed shape (R) and the other for wrinkled seed shape (r).

Usually organisms have two alleles for each trait. When the alleles of a pair are heterozygous, one is dominant and the other is recessive. The dominant allele is expressed and the recessive allele is masked. In the above example, round seed shape (R) is dominant and wrinkled seed shape (r) is recessive. Round: (RR) or (Rr), Wrinkled: (rr).

Another example - While considering height of the pea plant, we have two contrasting features i.e tall and short pea plant. So height is governed by two alleles - T and t.

Regards, Team Topperlearning