Quantitative Trait Loci Can Be Examined Using Pure-Breeding Parents and Measuring

Quantitative trait loci can be examined using pure-breeding parents and measuring a particular trait.If each allele makes an equal contribution to the phenotype,then the number of loci can be discerned.Bristle length in Drosophila behaves as a quantitative trait.If one parent has bristles of 30 nm and a second fly has bristles of 10 nm,then the F1 will have bristles of 20 nm.If the F1 flies are crossed to produce the F2 generation,the following classes of flies are observed.Use this data to answer these questions: a)How many different genotypes would be found among the flies with 10 nm bristles? b).How many different genotypes would be found among the flies with 30 nm bristles? c)How many different genotypes would be found among the flies with 15 or 25 nm bristles? d)How many loci are affecting this trait? e)If one wanted to find a physical marker that was linked to genes affecting bristle length,which flies would be most useful?
Number of F2 Flies Length of bristles
10 10
40 15
60 20
40 25
10 30