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NORWEGIAN UNIVERSITY OF SCIENCE AND TECHNOLOGY
Faculty of Natural Sciences and Technology
Department of Biology
Subject teacher: Jarle Mork (90973351), Hans Stenøien (91897592)
EXAMINATION IN: BI 3010
ENGLISH
DATE:
Points: 7.5
Number of pages: 5
Number of hours: 4
Permitted aids: Calculator HP 30S
Grades to be announced on: January 8., 2007
ALL QUESTIONS COUNT AS EQUAL
___________________________________________________________________________
English
Question 1.
Some very fundamental topics in population genetics theory were formulated already by the
pioneers in the field. Among these topics are the Hardy-Weinberg (H-W) theorem, the
Wahlund principle, and "Fisher's fundamental theorem on natural selection" (Fisher's
theorem).
a) Phrase the Hardy-Weinberg theorem in words.
b) Phrase the Wahlund principle in words.
c) Phrase Fisher's teorem in words.
Question 2.
Use the information in tables 1 and 2 (Appendix) and answer the following questions:
a) What are the allele frequencies for A and B in the samples?
b) What are the expected (according to H-W) genotypic numbers in the samples?
c) What are the chi-square (Goodness-of-fit test; G-o-f) values for each of the observed
genotype distributions?
d) How are degrees of freedom (DF) calculated in G-o-f tests?
e) What are the significance levels (P) for the observed genotype distributions in the samples
(use Appendix Table 2).
f) Show how you can use a chi-square RxC contingency table test and Table 2 to decide
whether the difference in allelic proportions in samples 1 and 2 is statistically significant, and
report your conclusion.
Question 3.
The so-called "Breeder's equiation" is a simple formula for estimating the expected response
(R) in a selection regime, using the heritability (h2) and the selection differential (S) when the
population mean and the truncation point (T) is known. (S can also be expressed as I*SDP,
where I is the difference (in SDP units) in phenotypic mean values between the population and
the selected group).
Assume the following scenario:
We want to improve the trait <mean length at age=2 years> in a population of farmed fish. In
the start population the phenotypic mean value is 40 cm with SDP=8 cm.
In one hypothetical experiment (Regime 1), individuals larger than 48 cm are selected for use
as brood stock for producing the F1 generation. In a second hypothetical experiment (Regime
2), the largest (by length) 20% of the individuals are used for producing F1.
a) What is the expected mean lenght at 2 years in F1 using Regime 1?
b) What is the expected mean length at 2 years in F1 using Regime 2?
Use Falconer's Table A (Appendix Table 3) as an aid.
Question 4.
a) Fig. 1 (Appendix Fig. 1) shows clinal variability in Adh allele frequencies in Australian,
North American and Eurasian Drosophila melanogaster populations. Each circle represents a
population, and solid part of circles represents the proportion of the Fast allele. How will you
explain the pattern observed?
b) Explain the main features of the “nearly-neutral” theory.
c) Explain how phylogenetic trees can be reconstructed by parsimony analysis.
d) What is a substitution model? Give examples of two commonly used nucleotide
substitution models and explain shortly how they differ.
APPENDIX
Table 1. Observed genotypic distribution at a locus in samples from two natural population of a diploid organism.
Sample 1
AA
40
Sample 2
66
Genotypes
AB
BB
120
40
110
Table 2. Critical values of chi-square.
24
N
200
200
qA
Allele freq.
qB
Goodness-of-fit test
chi-square and DF
P
Table 3. Falconer's table A
Fig 1