Biology 52 problem set E - Drosophila

 

[*hand in answers in recitations]

 

42)  a) In what cells and at what time is each of the following Drosophila genes expressed?

                        BICOID

                        NANOS

                        DORSAL

                        SNAIL

                        HUNCHBACK

 

            b) What phenotype is conferred by mutations in each of the genes?

            c) Does the phenotype in each case depend on the genotype of the mother or the genotype of the embryo?

 

43)  Put the following events in Drosophila development in the correct sequence:

                        a) expression of HOX genes

                        b) expression of gap genes

                        c) metamorphosis (larva to adult transition)

                        d) determination of imaginal disc cells

 

44)  a) What effect does the bicoid mutation have on Drosophila embryos?

            b) Where is the BICOID gene expressed? 

            c) Where is the Bicoid protein found?

            d) How would injecting extra BICOID mRNA into the anterior end of a Drosophila egg affect development?

            e) How would injecting extra BICOID mRNA into the posterior end of a Drosophila egg affect development?

 

45)  The Ultrabithorax gene controls the identity of the third thoracic segment.  What will happen if the Ultrabithorax gene is inactivated by mutation?  What will happen if a regulatory mutation causes misexpression of the gene in the second thoracic segment?

 

*46)  a) The diagram on the left shows where various genes are expressed in a cross-section of a wild-type blastoderm stage Drosophila embryo.  Using the diagram on the right, describe the location of the Dorsal protein at the same stage:

 

 

 

 

 

 

 

 

            b) What effect does Dorsal protein have on transcription of each of the following genes:

                        i) Snail

                        ii) Rhomboid

                        iii) Decapentaplegic (dpp)

            c) Among those genes that Dorsal turns on, which of these three is turned on by the lowest concentration of Dorsal protein?

            d) Which gene is expressed in future mesodermal cells?

            e) On the following diagram, indicate where the Rhomboid gene would be expressed in a snail twist homozygous double mutant embryo.

 

 

 

 

 

 

 

 

 

47)  a) What defects (if any) would Drosophila embryos in the following situations have? 

                        i) mother and embryo both homozygous mutant for dorsal

                        ii) mother homozygous mutant for dorsal, embryo heterozygous (+/-)

                        iii) mother and embryo both homozygous mutant for cactus

                        iv) mother and embryo both homozygous mutant for snail

                        v) mother homozygous mutant for snail, embryo heterozygous (+/-)

            b)         i) In some of the above cases, it may seem strange that the mother could possibly have been homozygous for a particular mutation,                             because that mother would have died during embryogenesis.  For which of these cases would that be a problem?

ii) How might one get around that problem experimentally?  In other words, how can one test the effect of a maternal mutation on offspring when that mutation should have killed the mother before she reached maturity?  Describe a genetic method for accomplishing this.