Recombination rates between three loci, L2, R, and W2, in corn are shown in the table.

Loci Recombination rate
L2 and R 35%
R and W2 17%
L2 and W2 18%

Use the recombination rates to arrange the three genes on the section of DNA.

1 = L2

2 = W2

3 = R

Question

Recombination rates between three loci, L2, R, and W2, in corn are shown in the table.

Loci	Recombination rate
L2 and R	35%
R and W2	17%
L2 and W2	18%

Use the recombination rates to arrange the three genes on the section of DNA.

1 = L2

2 = W2

3 = R

BlackTom AI · Accepted Answer

We are given recombination rates among three loci: L2–R = 35%, R–W2 = 17%, and L2–W2 = 18%. To arrange the three genes on a chromosome, we look for the smallest recombination rate to identify which pair is closest (i.e., adjacent). Here, the smallest rate is 17% for R–W2, so R and W2 should be adjacent. The remaining locus, L2, must be placed so that the distance to one of these adjacent pairs matches one of the listed rates.

- If R and W2 are adjacent, the distance between L2 and W2 is 18% (L2–W2) and the distance between L2 and R is 35% (L2–R). This is consistent with L2 being separated from the R–W2 block by the larger distance.
- Therefore, the correct linear order on the DNA strand is L2 — W2 — R, with the map distances L2 to W2 = 18% and W2 to R = 17%, and L2 to R = 35% (the sum of adjacent distances).

Now evaluate the given dropdown answers:
- If the first dropdown (position 1) chooses L2, that places L2 at the leftmost position in the trio, which is consistent with the L2–W2 adjacency (18%) being the nearer neighbor for L2. If the second dropdown (position 2) chooses W2, this places W2 immediately to the right of L2, forming the L2–W2 adjacency with a rate of 18%, which is correct in the L2–W2 link. This arrangement then leaves R to the right of W2, giving the R position as the third locus and matching R’s adjacency of 17% to W2 and 35% to L2. In short, L2 in spot 1 and W2 in spot 2 aligns with the correct overall order L2–W2–R.
- If the first dropdown selected W2 (and second selected something other than W2), the leftmost position would place W2 at the start, which would misplace the known adjacent pair (R–W2 is 17%, so W2 should be adjacent to R, not necessarily the far left). This would disrupt the correct adjacency pattern.
- If the first dropdown selected R, that would place R at the leftmost gene, which would imply the left-to-right order includes an L2–R distance of 35% as the immediate neighbor, contradicting the smallest recombination rate being between R and W2. This would not produce the correct adjacent pairing and would misrepresent the distances among the three loci.

In summary, the arrangement that matches all given recombination rates is L2 — W2 — R, with 18% between L2 and W2 and 17% between W2 and R. The dropdowns should reflect: 1 = L2 and 2 = W2, with 3 automatically being R, to reflect the correct linear order on the DNA strand.

01:447:380:17 GENETICS Week 10- In Person problem set_Fa25

Recombination rates between three loci, L2, R, and W2, in corn are shown in the table. Loci Recombination rate L2 and R 35% R and W2 17% L2 and W2 18% Use the recombination rates to arrange the three genes on the section of DNA. 1 = L2 2 = W2 3 = R

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