Download Practice exam (2010)

PCB5065 Fall 2010
Exam 4
Total value = 70 points
Name ____________________________________________
Question 1
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Question 2
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Question 3
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Question 4
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Important – please keep your answers short; confine your answers to the space
provided; do not write on the back of any pages !
PCB5065 Fall 2010
Exam 4
page 2 of 5
Name ____________________________________________
1. (15 pt) The questions below pertain to the genetic transformation of organelle genomes,
which presents some special challenges.
a) Transgenes are introduced into organelles via bombardment with DNA-coated particles
and inserted into the organelle genomes via homologous recombination. Immediately after
this occurs, the bombarded cells are heteroplasmic for the transgene. What genetic behavior
of organelle genomes allows for the eventual selection of homoplasmic organelle genome
transformants? Explain your answer.
b) Because organelle genome transformation occurs by homologous recombination, mutant
correction by homologous gene replacement is possible. Explain how you would select for
yeast cells in which a mutant gene essential for mitochondrial respiration had been
successfully replaced with a wild-type gene.
c) Because organelle genome transformation occurs by homologous recombination, mutant
correction by homologous gene replacement is possible. Explain how you would select for a
a chlamydomonas cell in which a mutant gene essential for chloroplast photosynthesis had
been successfully replaced with a wild-type gene?
PCB5065 Fall 2010
Exam 4
page 3 of 5
Name ____________________________________________
2) (15 pt) In mice, the imprinted insulin growth factor 2 (Igf2) gene is expressed from the
paternally-inherited chromosome. The maternally contributed gene is silent. The
complete loss of Igf2 function is viable, the mutant mice are just much smaller than wildtype mice.
a) If a 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.
b) If an Igf2 – / + male mouse is mated with a wild-type (Igf2 +/+) female mouse, what are the
expected frequencies of Igf2 genotypes and resulting phenotypes in the offspring?
Explain your answer.
c) If an Igf2 +/+ male mouse is mated with an Igf2 – / + female mouse, what are the expected
frequencies of Igf2 genotypes and resulting phenotypes in the offspring? Explain your
answer.
PCB5065 Fall 2010
Exam 4
page 4 of 5
Name ____________________________________________
3. (20 pt.)
3a) The major gene classes that act in drosophila development are: homeotic (segment
identity) genes, gap genes, maternal effect genes, pair-rule genes and segment polarity
genes. In the table below, list these classes of genes in the order that they come into play
during the drosophila developmental program (first =1, last=5).
3b) In the table below, indicate the general function of the proteins encoded by each gene
class (e.g. transcription factor, receptor, etc.)
3c) In the table below, indicate one phenotypic feature that is commonly observed in fly
larvae or adults that are homozygous for a loss-of-function mutation within each gene class
Order of
action in fly
development
Gene class
General function of protein
products
Loss-of-function mutant
phenotype in fly larva or
adult
1
2
3
4
5
3d) Which of the gene classes listed above are highly conserved in gene sequence and
gene product function, between insects and mammals?
3e) Which of the gene classes listed above have functions unique to drosophila and related
insects, and what developmental feature or advantage is conferred by those gene
functions?
PCB5065 Fall 2010
Exam 4
page 5 of 5
Name ____________________________________________
5. (20 pt.) The diagram below shows the ABC model describing the specification of different
floral organs in the four whorls of the arabidopsis flower. The spatial positioning of floral
organ identity gene (A, B and C) expression is shown, along with the resulting pattern
of floral organs.
A
B
B
A
C
C
sepal petal stamen carpel
x
y
z
5a) Based upon the ABC model diagrammed above, indicate which gene or combination of
genes that acts to specify:
Sepals
Petals
Stamens
Carpels
5b) Which two gene classes in the diagram above mutually repress each other’s expression ?
5c) Over x (above), use boxes to diagram the spatial distribution of remaining gene products if
B function is entirely lost by mutation; underneath your boxes, indicate the flower
structures that are predicted to develop. Just label them (e.g. sepal, petal, etc.); no
need to draw them.
5d) Over y (above) use boxes to diagram the spatial distribution of gene products and then
indicate the flower structures predicted to occur if C function is entirely lost by mutation.
5e) Over z (above) use boxes to diagram the spatial distribution of gene products and then
indicate the flower structure predicted to occur if A function is entirely lost by mutation.
5f) In the space below, briefly compare and contrast the nature of the plant floral organ identity
genes with the drosophila segment identity genes respect to their evolutionary origins
and functions.