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 located in genes 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:

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  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
 
 
 Based on these data, which of the following conclusions is most valid?
 
 
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 located in genes 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:
 
 
 
  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
 
 
 Based on these data, which of the following conclusions is most valid?
There are no QTLs affecting fruit size in this portion of chromosome 2.
Gene C is a QTL affecting fruit size.
Genes B and C are both QTLs affecting fruit size.
One or more genes in the region around gene C are QTLs affecting fruit size.
 
asked Nov 18, 2013 in Genetics by Piaso2245 (-45 points)
    

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