Genetics
Name: ___________________________
Biol 3300
In Drosophila, the genes plexus wings and speck body are at 100.5 mu and 107.5 mu,
respectively from the telomere on the Chromosome II.
a.) How many map units separate plexus wings and speck body?
b.) Draw out how you would create a female Drosophila, in Virtual Flylab, that is doubly
heterozygous for mutations in plexus wings and speck body. Assume that the mutant
phenotypes are autosomal recessive. Make the mutations in cis for the double
heterozygote. (hint: by the rules of Virtual Flylab, how will you design the P0 flies, and
which F1 flies will you select?)
c.) How would you make a double heterozygote that is in trans?
d.) If you take the first female het (the one in cis) and mate her to a plexus winged, speck
bodied male (a testcross male), what genotype and phenotype proportions among the
progeny do you expect (assume 1000 progeny, and include both “recombinant” progeny
and “non-recombinant” progeny)? [hint: make sure you do not mate the female het to a
brother!]
In Drosophila, speck body is on Chromosome II, while javelin bristles gene is on Chromosome
III. If you take a female who is heterozygous for speck body and javelin bristles, and mate her to
a test cross male, what genotype and phenotype proportions among the progeny do you
expect? (the heterozygous female is neither cis nor trans. Why?)
In Drosophila, the clot eyes gene is at 16.5 mu on the Chromosome II, while speck body is at
107.5 mu on the same chromosome. If you take a female who is heterozygous for clot eyes
and speck body (in cis), and mate her to a test cross male, what genotype and phenotype
proportions among the progeny do you expect? (hint: remember special rules about map
distances greater than 50 mu).
You will characterize the genes below by placing them into linkage groups (determine whether
they are nearby on the same chromosome). To do this you must:
a.) Determine whether they are AR, AD, XR, XD, or recessive lethal
b.) Test each of the genes in combinations of two for whether they assort independently:
a. For each pair of genes you test for linkage, create a double heterozygote and
mate the double heterozygote in a test cross.
b. Examine the resultant progeny for whether their proportions are consistent with
independent assortment or linkage.
c. If the two genes show linkage, then determine the map distance.
d. Check your answers with Dr. Chen-Quin.
Genes to test: dumpy wings, black body, purple eyes, spineless bristles, sepia eyes