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ff You cross two inbred tomato varieties with large (strain 1) and small (strain

ID: 42035 • Letter: F

Question

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You cross two inbred tomato varieties with large (strain 1) and small (strain 2) fruit size.  In the F2 progeny, you measure the average diameters of fruits on each plant and genotype them at 4 molecular markers A, B, C, and D which are situated in that order on chromosome 2.  You obtain the following average fruit diameters for each genotype at each of the four marker loci:

Based on these data, which of the following conclusions is most valid?

Loci B and C are both QTLs affecting fruit size.

Locus C is a QTL affecting fruit size.

One or more genes in the region around loci B and C are QTLs affecting fruit size.

Mean fruit diameter (cm.) Marker locus Variety 1 homozygote Heterozygote Variety 2 homozygote LOD score (>3.0 is significant) A 22 23 21 0.61 B 24 21 20 3.23 C 26 23 18 4.29 D 23 22 20 1.82

Explanation / Answer

Loci B and C are both QTLs affecting fruit size.

Loci B and C are both QTLs affecting fruit size.