NEET Biology question
Fruit shape in shepherd's purse (*Capsella bursa*) is of two types — triangular and top-shaped. Triangular fruit shape () is dominant over top-shape (). The following table summarises the results of several crosses:
Strain 1 × → All triangular Strain 2 × → 1 triangular : 1 top-shaped Strain 3 × → All top-shaped Strain 4 × → 3 triangular : 1 top-shaped
Which pair of strains possesses the genotype ?
Solution
Strain 1, crossed with , gives all triangular offspring, meaning it must be homozygous dominant, . Strain 2, crossed with , gives a 1:1 ratio, the classic signature of a test cross on a heterozygote, so Strain 2 is . Strain 3, crossed with , gives all top-shaped offspring,
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