1. PCB5065 Fall 2012 - Exam 4 - Chase Name __________________________________
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Question 1 ___________________________
Question 2 ___________________________
Question 3 ___________________________
Total ___________________________ out of 50 points
Important – please keep your answers short; confine your answers to the space provided; do not write on the back of any pages !

2. PCB5065 Fall 2012 Exam 4 Chase Name __________________________________
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1 (21 pt) In your own words, define or describe each of the following:
1-a) Hetroplasmy (as it pertains to organelle genetics)
1-b) Meiotic drive
1-c) Maternal effect gene
1-d) Epigenetics
1-e) Genomic imprinting
1-f) Paramutation
1-g) Gametophytic effect in plants

3. PCB5065 Fall 2012 Exam 4 Chase Name __________________________________
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2. (15 pt) In the human pedigree shown above, shaded individuals are affected by vision loss in young adulthood. Squares represent males and circles females. Roman numerals indicate generations and Arabic numerals indicate individuals.
2-a) Based upon the pedigree shown, could this vision-loss trait be the result of a recessive nuclear autosomal mutation? Explain why or why not.
3-b) Based upon the pedigree shown, could this vision-loss trait be the result of a genetic mutation in a maternal effect gene? Explain why or why not.
3-c) Based upon the pedigree shown, could this vision-loss trait be due to a mitochondrial gene mutation? Explain why or why not.

4. [from Munshi and Duvvuri J Genet Genom 434:93]
PCB5065 Fall Exam 4 Chase Name __________________________________
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enhancers
[from Munshi and Duvvuri J Genet Genom 434:93]
3 (15 pt) The diagram illustrates the expression patterns of an imprinted gene region in mammals. The insulin growth factor 2 (Igf2) gene is an imprinted gene. The paternal allele is expressed and the maternal allele is silenced. In mice, loss of Igf2 function leads to a small, but viable, mouse.
3-a) If a female mouse is heterozygous for a loss-of-function mutation at the Igf2 locus (genotype Igf2 -/+), will this mouse have a mutant or wild-type phenotype? Explain your answer.
3-b) If the Igf2 -/+ female mouse is mated with a wild-type (Igf2 +/+) male mouse, what are the expected progeny genotypes and phenotypes? Explain your answer.
3-c) If an Igf2 +/+ female mouse is mated with an Igf2-/+ male mouse, what are the expected progeny genotypes and phenotypes? Explain your answer.
Fig. 2 Schematic illustration of the Igf2/H19 domain on the two parental chromosomes, where the H19 gene is maternally expressed and Igf2 is paternally expressed under normal conditions The differentially methylated region is located upstream of H19 gene. Enhancers are shown as triangles, downstream of H19. In the maternal allele the zinc-finger nuclear factor CTCF interacts with unmethylated DMR and provokes a maternal specific enhancer blocking the activity of DMR and allowing only H19 expression. In contrast, on the paternal allele, the CTCF cannot bind because of DMR methylation. As a result the enhancer blocking activity is lost and the downstream enhancers are able to drive expression from paternally inherited Igf2 gene over a long distance. Moreover, DMR and H19 gene are methylated and thereby H19 gene gets silenced on the paternal allele. (Drawing not drawn to scale)

5. Developmental genetics (50 pts) Name____________________
1. (10 pts) Recall that the bicoid (bcd) mutant produces embryos that lack anterior features, and the kruppel (kr) mutant produces embryos that have a "gap" in middle of the fly body plan. Describe the expected progeny of the following crosses (where the genotype of the female fly is on the left). Give expected ratios if more than one phenotype is expected. One of these crosses is not feasible using conventional genetics and a typical loss-of-function mutant allele. Explain.
bcd/bcd X BCD/BCD
BCD/bcd X bcd/bcd
bcd/bcd X BCD/bcd
Kr/kr X Kr/kr
kr/kr X Kr/kr
2. (10 pts) Describe the two essential components of the genetic module that translates a smooth gradient of BCD protein concentration into a sharp boundary of Hb expression in the fly embryo. Both components are associated with distinct structural features of the upstream regulatory sequences of the Hb gene. Explain.
3. (5 pts) Recall that the second stripe 2 of the Even-Skipped expression pattern is determined by interactions of Bicoid, Hunchback, Giant, and Kruppel. Which of these factors are activators and which are repressors? In a kruppel mutant embryo, would you expect stripe 2 to 1) disappear, 2) broaden in the posterior direction, or 3) broaden in the anterior direction?
4. (10 pts) Key segment polarity genes that establish the boundary between anterior and posterior compartments of segments include patched, engrailed, wingless and hedgehog.
Which genes encode 1) transcription factors, 2) secreted peptides, and 3) membrane receptors?
The wingless mutant has a distinctive visible segment polarity phenotype in the larval stage. Explain.
In the adult fly, partial loss-of-function alleles of the engrailed gene have a distinctive polarity phenotype in the wing. Explain.
5. a. (3 pts) Professor Harfe emphasized fast generation time was a key feature of model organisms. What unusual features of fly embryo segmentation probably resulted from evolutionary selection for a fast generation time?
b. (2 pts) Professor Harfe mentioned that compared to other model organisms Drosophilia was not conducive to researchers taking vacations. Why not?
6. (10 pts) Diagram the ABC model for determination of floral organ identity in plants. Include a diagram illustrating the phenotype of "A" class mutants. The model invokes two general principles that are shared by the homeotic (hox) genes in animals. Explain.