EasyBiologyHigh School (9–10)GeneralHeredity and Evolution › Heredity and InheritanceConceptualBoard Exam
An F1 pea plant from a dihybrid cross has the genotype RrYy…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
An F1 pea plant from a dihybrid cross has the genotype RrYy. How many kinds of gametes does it make? Write them. Why are there that many?
Need a reminder? The key ideaShow
In a dihybrid cross, pure round yellow (RRYY) crossed with pure wrinkled green (rryy) gives an F1 all RrYy, round and yellow. An RrYy plant makes four gametes, RY, Ry, rY and ry. The F2 has round yellow, round green, wrinkled yellow and wrinkled green in the ratio 9 : 3 : 3 : 1, so the two traits are inherited independently.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. Shape. A gamete gets either R or r.
Step 2. Colour. It also gets either Y or y, independently of the shape copy.
Step 3. Pairs. kinds: RY, Ry, rY and ry.
Answer: kinds of gametes, because the two genes go into gametes independently.
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