Genetics Question

[mgystudent]

Hi Everyone,

I know this is a random question, but I'm doing a course for my masters to learn about genetics mapping and I could use some help understanding recombination mappnig.  So we were given this question:   Mutations in the old-1 gene cause extension of the C. elegans life span. Mutants defective in the let-513 gene die as young larvae. Suppose you have a strain of genotype dpy-10 old-1 / unc-4 let-513 II, which is wild-type in phenotype, and you identify 33 adult Unc animals among the progeny of several heterozygotes. You find that 25 of the 33 Uncs segregate the Old phenotype upon self-fertilization, but none segregates the Dpy phenotype. a. What is the order of the 3 genes along the chromosome? b. If unc-4 maps 2 cM from old-1, what is the map distance between unc-4 and let- 513?

Would anyone be able to help me solve this?  Thanks!