GENETICS TEST 2 - FALL 2014(2)
Zombie Genetics!
This test has two parts. In Part 1, answer 4 of the 5 questions (15 pts each). Please indicate the
questions you want me to grade. If there is any uncertainty I will grade the first four. All
students must complete Part 2 (25 pts). Part 3 will make up 15% of your test grade.
NAME:
Zombie Riddle (Answer at the end of the
test....): What do zombie turkeys eat?
Test 1 Background Information.
In honor of the recent Halloween festivities, we will now turn our attention away from
Scotland...and into much deeper earth. Graves. The home of the zombies.
Many different research labs have tried to isolate the exact causative agent of zombies, but it
remains elusive. What is known is that an external agent of some sort, perhaps viral, initially
causes wholesale somatic mutations, creating proto-zombies that still retain some of their
humanity. Unfortunately, the mutations have slow, pleiotropic effects that ultimately give rise to
the full zombie phenotype. This test analyzes just a few of those mutations.
A codon table that contains the one letter amino acid abbreviations can be found at the end of
this test.
Part One. Complete 4 of the following 5 questions. Please show all work and indicate
which questions you want me to grade.
Question One: One of the very first phenotypic changes seen in zombies is a slight green cast to
the skin...a sign of the gradual rotting to come. The biochemical pathway for the synthesis of
this color is shown below:
Colorless
Gene A
Yellow
Blue
Gene B
Colorless
What phenotype (color) would you expect flowers to have if they were homozygous for the
following mutations? Explain each answer
1) A down promoter mutation in gene A
2) An up promoter mutation in gene B
3) A frameshift mutation early in gene A
Question Two: The coding strand of the 5’ end of the gene for the gray-matter-oxidizing -andsliming-substance (GROSS) gene is shown below. As in humans, the first amino acid in all
zombie proteins is methionine.
5’ CCCGCGTGCC
TCCTCCCAAG
GCAGAAACCC
TCGATGCCAT
AAGAAGGCAG
AAATCGGGTC
GTTCTTACCC
CGGAGCATTT
GGGGGCCAAG
CGTGATGGCG
TAGTTTGGGT
TGAGATCGGG
GGCCTGCCCC
GTGCCTGAAG
GGCGGGCTGC
GATGAGAGGT
GTGATGGAGG
TGCTACCAAG
GCGCCGCCGC
CTGCCGGGTC
TTGCCGCTAT
TTCATGGGGA
GAAGGCAGCA
GTTTTGCTTT
TTCCGGAAGT
TGCTACGGCA
GTCCTGTAGG
AGGGTATCGG
TGGCACGCTG
TGCATGGAAA
GGGTCTCGTC
CCGCGGGGCT
GAAGCCATGT
GAAGGCTATG
CATGGAGCCA
3’
Circle the start codon for this gene.
Using the codon table at the end of this test, give the single letter abbreviation for the
next six amino acids (after the start codon) that are coded for by this gene.
Question Three: Another early phenotype that proto-zombies display is curled fingers, which is
due to a single point mutation in the zombieflexin-III gene. The effects of this gene mutation
increase over time until the wrists, elbows and shoulders also become impacted.
The Western blot above shows zombieflexin III expression in a variety of different individuals.
Lanes 1 and 2 show expression in normal male and female humans, respectively. Lane 3 shows
expression in proto-zombies and Lane 4 shows expression in zombies. M is a molecular weight
marker.
1. What is the approximate size of the zombieflexin III protein in kD (kiloDaltons)?
2. Your other lab partner states that they think the point mutation is a nonsense mutation. What
is a nonsense mutation?
3. Do you think that nonsense mutation could be responsible for the patterns of expression you
see in the Western blot? Why or why not?
4. Propose an alternative hypothesis to account for the results you see in the Western blot.
Question Four: Occasionally, zombies are observed that display gray, rather than green skin. It
is postulated that this phenotype is due to a conditional mutation in the green conversion factor-3
gene (also needed in the green skin pathway, but distinct from the genes in question 1).
Specifically, it is believed that eating the brains of vegetarians, rather than those of meat-eaters,
will decrease the transcription of this gene, resulting in a gray color.
In order to test this hypothesis, green and gray zombies were fed the brains of vegetarians and
meat-eaters, and then Northern blots were run to analyze the resulting expression of green
conversion factor-3 (Yes, it would have been easier to just observe the zombie color to see if it
changed, but what fun would that be?) Lane 1 contains a 290 Kb size marker. Lanes 2 and 3
show the expression of gene conversion factor-3 in green zombies fed meat-eater (lane 2) versus
vegetarian (Lane 3) brains. Lanes 4 and 5 show the expression of gene conversion factor-3 in
gray zombies fed meat-eater (lane 4) versus vegetarian (Lane 5) brains.
1. Are these results consistent with the conditional mutation described above (yes or no)?
2. Explain your answer to 1
3. Give a possible alternative hypothesis for the results seen in the Northern blot.
Question Five: Dogs can also become zombies, although it is hard to tell the difference at
times, depending on the breed. For some unknown reason, the enzyme Glucose-6-phosphate
isomerase seems to be critical to the transformation to the zombie phenotype. Part of the amino
acid sequence for the wild type glucose-6-phosphate isomerase enzyme is shown below, along
with the same part of the protein as produced by four mutant zombie dogs, each of which
contains a single, different point mutation. For each of the mutants, give a single DNA base
change that could account for the observed change, and tell whether that change is a missense,
nonsense, silent or frameshift mutation. A codon table can be found at the end of this test.
Wild Type: Met-Glu-Lys-Ser-Ala
Mutant 1: Met-Glu
Mutant 2: Met-Lys-Lys-Ser-Ala
Mutant 3: Met-Glu-Lys-Ser-Ala
Mutant 4: Met-Arg-Glu-Ile-Gly
Part Two: You must answer this question.
Female zombies and male zombies differ, like their human counterparts, in their sex
chromosomes. Female zombies are XX and male zombies are XY. In male zombies, a Y-linked
gene that is mutated leads to the expression of the yellow eye gene early in the proto-zombie
stage, but only if the Sox-9 transcription factor is present. Female zombie eyes do not normally
turn yellow due to the expression of beta-catenin, which is normally only expressed in females
and completely inhibits the expression of Sox-9. Recently, scientists have discovered the
following yellow-eyed female zombie:
Describe how three different point mutations (they must either have different impacts on gene
expression, such as decreased transcription, shortened protein, etc.), or they can have the same
impact, but must be in different genes) could have caused yellow eyes in this female zombie. Be
very explicit. For each of your three mutations, 1) name the mutation type and the gene that it is
impacting, 2) tell where in the gene the mutation is located, 3) state whether it would impact the
transcription or translation of the particular gene 4) tell how it would impact transcription or
translation and 5) explain how the mutation would cause yellow eyes to form in a female zombie.
Answer to zombie riddle...........