Quantitative Genetics - PowerPoint PPT Presentation

1 / 23
About This Presentation
Title:

Quantitative Genetics

Description:

Quantitative Genetics. julian_christians_at_sfu.ca. See also Chapter 20 in. Griffiths et al. ... Quantitative genetics theory - basis for breeding programmes ... – PowerPoint PPT presentation

Number of Views:72
Avg rating:3.0/5.0
Slides: 24
Provided by: JulianCh4
Category:

less

Transcript and Presenter's Notes

Title: Quantitative Genetics


1
Quantitative Genetics
  • julian_christians_at_sfu.ca
  • See also Chapter 20 in
  • Griffiths et al.
  • Introduction to Genetic Analysis

2
Quantitative Genetics
  • Continuous phenotypic variation within
    populations
  • Whole organism level
  • Causes of variation
  • Genes vs. environment
  • Interactions between genes and environment
  • Components of genetic variation
  • Components of environmental variation

3
Why is quantitative genetics important?
  • Medicine
  • Disease variation
  • Complex disorders
  • caused by multiple genetic and environmental
    factors
  • Understanding genetic vs. environmental causes
  • prevention
  • genetic counselling
  • genetically-tailored treatments

4
Why is quantitative genetics important?
  • Agriculture
  • Economically important traits quantitative
    traits
  • Quantitative genetics theory -gt basis for
    breeding programmes
  • Environmental variation reduces efficiency of
    selection

5
Why is quantitative genetics important?
  • Consequences of inbreeding and outcrossing
  • Agriculture inbred lines, hybrids, F1s
  • Conservation endangered species, captive
    breeding programmes

6
Why is quantitative genetics important?
  • Evolution
  • Natural selection requires heritable variation
    for traits
  • What are the forces that maintain variation
    within populations?
  • Balance between selection, drift and mutation
  • Balancing selection?

7
Why is quantitative genetics important?
  • Evolution
  • Does evolution proceed by small steps or big
    jumps?
  • What is the relative importance of pre-existing
    variation vs. new mutations?
  • Do genetic correlations between traits pose
    constraints on evolution?

8
History
  • Around 1900, there were two camps
  • Biometricians
  • Continuous traits
  • Mendelians
  • Discrete traits

Are discrete traits inherited in the same way as
quantitative traits?
9
History
  • Reconciliation
  • Multiple loci (genes) contribute to variation!

Is variation caused by a few loci of large
effects or many loci with small effects?
10
Heritability
Measured using resemblance between relatives
h2 genetic variation phenotypic variation
11
  • QTL
  • quantitative trait locus
  • region of chromosome that contributes to
    continuous variation

12
Questions
  • Is variation caused by a few loci of large
    effects or many loci with small effects?
  • To what extent do individual genes affect
    variation in different traits?
  • Are the same genes responsible for variation in
    different populations/ species?
  • What are the genes responsible for variation and
    adaptation?

13
phenotype
genetic markers
14
Basis of QTL mapping
15
(No Transcript)
16
(No Transcript)
17
Statistical Support
18
Problems
  • Mapping resolution is limited by recombination,
    which is limited by the number of individuals in
    cross or pedigree
  • Small effects are difficult to detect

19
Approaches
  • Controlled crosses of inbred or outbred lines
  • Pedigrees
  • Population-wide

Suitable for natural populations
20
Statistical Support
21
My work QTL affecting size in mice
Statistical Support
22
PAPP-A2
  • enzyme that cleaves an insulin-like growth factor
    binding protein (IGFBP-5)
  • IGFBPs modulate the effects of insulin-like
    growth factors

23
Interested in studying the physiological and
genetic mechanisms underlying variation within
species?Contact me!julian_christians_at_sfu.ca
Write a Comment
User Comments (0)
About PowerShow.com