In a testcross involving F1 dihybrid flies, more parental-type offspring were produced than the recombinant-type offspring. This indicates
- Both of the characters are controlled by more than one gene
- The two genes are linked and present on the same chromosome
- The two genes are located on two different chromosomes
- Chromosomes failed to separate during meiosis
Answer
(2) The two genes are linked and present on the same chromosome
Solution
If the two genes assorted independently, a dihybrid testcross would give parental and recombinant types in equal numbers (1 : 1 : 1 : 1).
⇒ An excess of parental-type offspring means the parental gene combinations tend to stay together.
∴ As per NCERT (Morgan's experiments on Drosophila), the two genes are linked, i.e. present on the same chromosome.
Answer: (2)