alleryWhat is the genotypic ratio obtained when a heterozygous tall pea plant (Tt) is self-pollinated?
A3 : 1
B1 : 2 : 1
C1 : 1
D9 : 3 : 3 : 1
Answer & Solution
Correct answer: B. 1 : 2 : 1
1. Self-cross Tt x Tt.
2. Gametes from each parent are T and t.
3. Punnett square gives one TT, two Tt and one tt.
4. Writing genotypes in order gives 1 TT : 2 Tt : 1 tt, that is 1 : 2 : 1, option B.
5. The 3 : 1 in option A is the phenotypic ratio, not the genotypic ratio.
_Source: Samacheer Kalvi (TN SCERT) Class 10 Science, Unit 18 Genetics "Monohybrid Cross", p.269_
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