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Mid Exam November 2017, questions
BIOL2151 (Australian National University)
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Biology Teaching and Learning Centre
EXAMINATION
Semester 2 - Mid-Semester
BIOL2151_BIOL6006 Semester 2 Principles of Genetics
Examination Duration:
120 minutes
Reading Time:
15 minutes
Exam Conditions:
Central Examination
Students must return the examination paper at the end of the examination
This examination paper is not available to the ANU Library archives
Materials Permitted In The Exam Venue:
(No electronic aids are permitted e.g. laptops, phones)
Calculator (non programmable)
Materials To Be Supplied To Students:
Scribble Paper
Instructions To Students:
This exam consists of two parts.
Section A: Answer 4 of the 6 questions (40 marks).
Section B: Answer 3 of the 4 questions (60 marks).
Answer all questions on the exam paper.
Please do not remove examination papers from the room.
Illegible handwriting on exam papers will not be marked!
This is an example of a mid-term exam and does not
contain a full set of questions.
Semester 2 - Mid-Semester Sample Exam
BIOL2151_Semester 2 Principles of Genetics
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SECTION A
Describe 4 of the 6 topics with short notes. Define all terms, where applicable use
examples, diagrams and tables and show relevant formulae. (40 marks, each topic of
equal value)
1) VNTRs and STRs and their respective advantages and disadvantages for forensic analyses.
3) Outline the steps and features of Sanger DNA sequencing and compare with Next
Generation Sequencing (NGS) methods.
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BIOL2151_Semester 2 Principles of Genetics
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5) Population substructure and population assignment, and examples of their relevance and
application in forensic analysis and wildlife research.
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SECTION B
Answer 3 of the 4 questions. (60 marks, each question of equal value)
7. Complete all parts of this question showing all formulae and calculations (20 marks)
On the graph below:
a) Plot the change in the Fixation index F over multiple generations of selfing by reference to
the scale on the left-hand Y axis. Assume the starting population consists of genotypes in
Hardy-Weinberg Equilibrium at a hypothetical A locus with two alleles in equal frequency.
b) Plot the corresponding predicted Observed Heterozygosity Ho and the Expected
Heterozygosity He values for each generation by reference to the scale on the right-hand Y
axis.
1.00_
_0.50
0.75_
F 0.50_
_0.25
Het
0.25_
0.00_
_0.00
0
1
2
3
4
5 6 7
Generation
8
9
10 11
c) Summarize the patterns you have plotted and explain why these patterns are observed.
Predict the pattern of allele frequency change over the eleven generations.
d) Give the formula for calculating the Fixation index F and show from first principles the
range for this index. Interpret the meaning of F at its extreme and intermediate values.
e) While selfing is the most extreme form of inbreeding, what general predictions can you
make about the genetic consequences of inbreeding?
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9. Complete all parts of this question showing all formulae and calculations (20 marks)
All Californian condor individuals homozygous for the chondrodystrophic dwarfism gene
(dwdw) die around hatching. In this biallelic system the recessive allele has an unusually high
frequency of approximately 0.17. Estimate the expected frequencies for ALL genotypes at
this locus under:
a) Random mating F = 0
b) Intermediate inbreeding F = 0.5
c) Complete inbreeding F = 1
d) Calculate the ratio of the homozygous recessive condition under complete inbreeding
(F=1) relative to random mating (F=0). What conclusions can you draw?
e) In light of the above findings, define inbreeding, and identify the population level genetic
changes that occur as a result of inbreeding.
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f) Define inbreeding depression (IBD), identify its probable cause and give examples of
reproductive traits impacted by IBD.
g) Using examples to illustrate, identify strategies to mitigate potential problems arising from
inbreeding.
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10. Complete all parts of this question showing all formulae and calculations (20 marks)
Late one evening in Canberra a serious assault is committed leaving both the victim and the
assailant seriously injured. Subsequently, a suspect was apprehended based on non-DNA
evidence. The Australian Federal Police (AFP) successfully obtained two different DNA
profiles from the blood left at the crime scene. One DNA profile matched the victim, the other
was assumed to be from the assailant. The AFP now plans to use this DNA evidence to help
secure a conviction of the suspect.
STR DNA profiles of the victim and suspect for 3 loci: THO, VWA and D21
Victim
Suspect
THO
187
176
VWA
159
171
191
180
D21
240
250
163
175
244
258
Allele frequencies based on random DNA samples from the Canberra region
Locus
THO
Allele
176
180
183
187
191
Locus
VWA
Freq
0.4
0.3
0.1
0.1
0.1
Allele
155
159
163
167
171
175
Freq
0.1
0.3
0.3
0.1
0.1
0.1
Locus
D21
Allele
Frequency
236
0.1
240
0.2
244
0.3
248
0.1
250
0.1
254
0.1
258
0.1
Template for calculating DPP for victim and suspect based on the 3 STR loci.
Genotype
Alleles in
Genotype
pi
Semester 2 - Mid-Semester Sample Exam
Genotype
Alleles in
Genotype
pi
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a) Give the formula for computing the DNA profile probability (DPP). Then, using the
template above complete the calculation of DPP for both the victim and the suspect.
b) Record the DPP values for victim and suspect below.
c) How many individuals would you expect to have the same DNA profile as the suspect
within the Canberra region (assume a population size of 360,000)? Show your calculation.
d) Interpret in plain English the meaning of the DNA profile probability (avoid the Defense
and Prosecutor fallacies).
e) Outline in full the genetic assumptions that you have made in calculating the DNA profile
probability.
f) What do you conclude about the weight of the DNA evidence? How would you strengthen
your case? Justify your answer.
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