Question

Some people can roll their tongue and this is a genetically controlled auto-somal
dominant character. [Roller = RR / Rr and Non-roller = rr]
A child who can roll the tongue has one brother who is a non-roller and two sisters who
are rollers. If both the parents are rollers, the genotypes of their parents would be ____.
i) RR x RR ii) Rr x Rr iii) RR x rr iv) rr x rr

Answer 1

If both the parents of the child are rollers (RR/Rr) then the genotypes of their parents can be Rr x Rr as only then you can get RR, Rr and rr.

From the problem statement one can say that the child is roller (RR/Rr), his brother is non-roller (rr), two sisters are rollers (RR/Rr).

Therefore, from the problem statement it can be said that out of the four options option ii.) is the correct one.