With the help of a table show the genotypes bearing genotypic ratio two (2) produced in F₂ generation as a result of a cross between a pea plant having pure round yellow coloured seed (RRYY) and another pea plant having pure wrinkled green coloured seed (rryy).
In this dihybrid cross RRYY × rryy, all F₁ plants are RrYy.
Selfing of F₁ (RrYy × RrYy) produces F₂ with 9:3:3:1 phenotypic ratio and a 1:2:2:4:1:2:1:2:1 genotypic ratio.
The genotypes which occur with frequency “2” in F₂ are shown below:
| Genotype | How it appears in F₂ |
|---|---|
| RR Yy | From YR × RY and Yr × RY gamete combinations (2 out of 16) |
| Rr YY | From YR × yR and YR × yR combinations (2 out of 16) |
| Rr yy | From yr × Yr and yr × Yr combinations (2 out of 16) |
| rr Yy | From yR × yr and yR × yr combinations (2 out of 16) |
| rr Yy | Thus each of these genotypes has genotypic ratio 2 in F₂. |
More WBBSE Hard level questions
Explain the following two terms related with heredity: (a) Genotype (b) Hybridization
In which of the following crosses, will the F1 generation seed's tall and dwarf traits appear in a 1:1 ratio? (a) Tt x Tt (b) TT x Tt (c) TT x tt (d) Tt x tt
What will be the phenotypic ratio of progeny obtained from the hybridization between YyRR and YYrr genotypes? (a) 2:1 (b) 1:2 (c) 2:2 (d) 1:4
If a population undergoes three generations, and if each generation consists of only males, what is the probability that females will be present in the fourth generation? (a) 100% (b) 0% (c) 50% (d) 75%
With the help of an example explain how the phenotypic and genotypic ratios found in F2 generation of certain hybrid crosses indicate exception to Mendel's first law of heredity.
Explain the following two terms related with heredity — (a) Allele (b) Locus
An inherent trait of organisms is the prodigality of reproduction; as a result, the number of organisms increases in a geometric proportion - justify the validity of the statement with two proper examples.
Write two reasons behind the selection of pea plants by Mendel for his experiments on heredity.
"Some phenotypes may have multiple genotypes and some other phenotypes may have a single genotype" — Justify the statement from the results derived from the dihybrid experiment in the case of the pea plant.
Write two causes behind Mendel's success in conducting experiments on heredity.
Prove the authenticity of the statement — "The phenotypic and genotypic ratio remain identical in case of Incomplete Dominance".
State Mendel's second law of heredity
