Question

In a trihybrid cross, the different types of genotypes obtained in the F₂ generation is

• A. 8
• B. 18
• C. 27
• D. 36

Answer 1

Answer: (C)

In a monohybrid cross, there are 3 types of genotypes produced in the F₂ generation: AA, Aa, aa. In a dihybrid cross, there are $3\times 3=9$ types of genotypes produced in the F₂ generation: AABB, AaBB, aaBB, AABb, AaBb, aaBb, AAbb, Aabb, aabb. In a trihybrid cross, there are $3\times 3\times 3=27$ types of genotypes produced in the F₂ generation (number of different F₂ genotypes is 3n) and they are: AABBCC, AaBBCC, aaBBCC, AABbCC, AaBbCC, aaBbCC, AAbbCC, AabbCC, aabbCC, AABBCc, AaBBCc, aaBBCc, AABbCc, AaBbCc, aaBbCc, AAbbCc, AabbCc, aabbCc, AABBcc, AaBBcc, aaBBcc, AABbcc, AaBbcc, aaBbcc, AAbbcc, Aabbcc, aabbcc.