Download Practice exam (2012)

PCB5065 Fall 2012 - Exam 4 - Chase
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Name __________________________________
Question 1
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Question 2
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Question 3
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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 !
PCB5065 Fall 2012 Exam 4 Chase
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Name __________________________________
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
PCB5065 Fall 2012 Exam 4 Chase
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Name __________________________________
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.
PCB5065 Fall 2012 Exam 4 Chase
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Name __________________________________
enhancers
[from Munshi and Duvvuri J Genet
Genom 434:93]
enhancers
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.
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.