Genetics!!

[craig-oy]

Hey i'm having lots of trouble with this question. Its on a practice final exam and he didnt give the answers so i dont know.

We are given these true breading stocks of D. Melanogaster: 1) vg-/vg-; 2) w-/w-; 3) ry-/ry-; 4) Bl-/Bl- and 5) +/+ and Cbc+/Cbc+ (obtained from a transgenic insert using transposable elements)
Bl and Cbc are dominant

"Design a series of crosses (using those given) to show that the Cbc+ transgene insert is 5 Map units from the Bl locus. Define the phenotypes and genotypes of the parents and expected progeny for each cross you undertake. Also, define the expected frequency of each class of progeny.



Okay so we are given 3 sections for crosses. I would have though you could cross the homozygous Cbc+ and a homozygous Bl- flies and then obtain the progeny which would be: Cbc+/cbc- Bl-/Bl+. Then test cross it and from here you would be able to see that the progeny occupy only 5 map units (5% of hte total progeny)

Am i on the right track?> tahnks alot