Question

(1)

Rice yield is a quantitative trait. Imagine that rice yield is controlled by four additive allleles, A, B, C, and D.

Come up with an example cross of two different strains of rice that each produce an intermediate yield, and that when crossed, produce progeny that are also intermediate.

(2) Rice yield is a quantitative trait. Imagine that rice yield is controlled by four additive allleles, A, B, C, and D.

Next, come up with an example cross of two different strains of rice that each produce an intermediate yield, but that when crossed, produce progeny that range from below average (but not lowest) yield to above average (but not highest) yield.

Answer 1

Answer 1:

Given that there are four additive alleles, namely A, B, C and D. It is said that crossing of two parents yields an intermediate, and that crossing of intermediate yields an intermediate too.

Intermediate individual will have 4 dominant genes. One possible cross which can yield such results is:

Parents: AABBccdd × AABBccdd

Gametes : ABcd from each parent.

	ABcd
ABcd	AABBccdd

F1: AABBccdd (intermediate trait value, as it has 4 dominant genes).

F1 × F1 : AABBccdd × AABBccdd

The cross would be same as above, and result would be:

F2: AABBccdd (intermediate trait value)

Answer 2:

For the second question, we need to choose such parents that F1 is intermediate, but F2 trait value ranges from below average to above average yield.

F1 should have 4 dominant alleles, whereas F2 should have anywhere in between 2-7 dominant alleles.

Parents: AABBCCdd × AAbbccdd

Gametes: ABCd, and Abcd

F1: AABbCcdd (intermediate trait value)

F1 cross: AABbCcdd × AABbCcdd

F1 gametes:

ABCd, ABcd, AbCd and Abcd.

The cross can be shown as:

Note that none is having lowest trait (i.e. none is aabbccdd) or highest trait (i.e. AABBCCDD) in F2.

(Kindly upvote if the answer helped).