Question

Fruit shape in shephered's purse (Capsella bursa) two typestriangular and top-shaped. Triangular fruit shape (T) is dominant over top-shape (t). Following table summarises the results of several crosses.

Cross	Result
Strain 1 x tt	All triangular
Strain 2 x tt	1 triangular : 1 top-shaped
Strain 3 x tt	All top-shaped
Strain 4 x tt	3 triangular : 1 top-shaped

Which pair of strains possess the genotype Tt?

• A. Strains 2 and 3
• B. Strains 2 and 4
• C. Strains 1 and 3
• D. Strains 1 and 4

Answer 1

The correct option is B Strains 2 and 4

Fruit shape in shepherd's purse (Capsella bursa) two types triangular and top-shaped. Triangular fruit shape (T) is dominant over top-shape (t). Since one individual in all crosses has the recessive genotype, they will transfer only the recessive gamete to the offspring. So, both the dominant and the recessive genotypes will occur in the offsprings only when the other individual is a heterozygote (Tt). In such cases if the dominant gamete is transferred the offspring will have the dominant phenotype and if the recessive gamete (t) is transferred the offspring will have the recessive phenotype. Such cases of both phenotypes being seen are only in case of strain 2 and 4. So, the correct option is 'Strain 2 and 4'.