Presentation is loading. Please wait.

Presentation is loading. Please wait.

CENTER FOR BIOLOGICAL SEQUENCE ANALYSIS Molecular Evolution Course #27615 Anders Gorm Pedersen Molecular Evolution Group Center for Biological Sequence.

Published by Modified over 9 years ago

Similar presentations

Presentation on theme: "CENTER FOR BIOLOGICAL SEQUENCE ANALYSIS Molecular Evolution Course #27615 Anders Gorm Pedersen Molecular Evolution Group Center for Biological Sequence."— Presentation transcript:

1 CENTER FOR BIOLOGICAL SEQUENCE ANALYSIS Molecular Evolution Course #27615 Anders Gorm Pedersen Molecular Evolution Group Center for Biological Sequence Analysis Technical University of Denmark (DTU) gorm@cbs.dtu.dk

2 CENTER FOR BIOLOGICAL SEQUENCE ANALYSIS Neutral Theory of Molecular Evolution Evolution is a two-step process: 1.Mutation (random) 2.Selection (non-random) Detrimental mutation =>negative selection =>Mutation not seen Beneficial mutation =>positive selection =>Mutation seen

3 CENTER FOR BIOLOGICAL SEQUENCE ANALYSIS Selectionist Views of What Drives Molecular Evolution Majority of all mutations are detrimental and not seenMajority of all mutations are detrimental and not seen Most observed mutations have adaptive valueMost observed mutations have adaptive value Classical school:Classical school: –Single predominant version of gene (“wild type”) present in population –Natural selection rapidly fixates new, advantageous mutations Balance school:Balance school: –Appreciable amount of polymorphism in gene pool –Polymorphism maintained actively by natural selection (e.g., sickle cell anemia)

4 CENTER FOR BIOLOGICAL SEQUENCE ANALYSIS Neutralist Views of What Drives Molecular Evolution Electrophoretic studies in 1960’s showed much higher polymorphism than anticipated by either classical or balance school selectionistsElectrophoretic studies in 1960’s showed much higher polymorphism than anticipated by either classical or balance school selectionists Kimura and others proposed the “Neutral Theory of Molecular Evolution”.Kimura and others proposed the “Neutral Theory of Molecular Evolution”. Detrimental mutation => negative selection => Mutation not seen Neutral mutation => no selection => Mutation may be seen (genetic drift) Beneficial mutation => positive selection => Mutation seen

5 CENTER FOR BIOLOGICAL SEQUENCE ANALYSIS Difference Between Selectionist and Neutralist Views of Evolution Selectionist view: Most observed mutations represent functional innovation Neutralist view: Most observed mutations represent conservative changes, changes in unimportant regions

6 CENTER FOR BIOLOGICAL SEQUENCE ANALYSIS All Agree that Adaptations are Caused by Natural Selection

7 CENTER FOR BIOLOGICAL SEQUENCE ANALYSIS All Agree that Adaptations are Caused by Natural Selection

8 CENTER FOR BIOLOGICAL SEQUENCE ANALYSIS All Agree that Adaptations are Caused by Natural Selection

9 CENTER FOR BIOLOGICAL SEQUENCE ANALYSIS All Agree that Adaptations are Caused by Natural Selection

10 CENTER FOR BIOLOGICAL SEQUENCE ANALYSIS All Agree that Adaptations are Caused by Natural Selection

11 CENTER FOR BIOLOGICAL SEQUENCE ANALYSIS The molecular clock

12 CENTER FOR BIOLOGICAL SEQUENCE ANALYSIS Genetic drift Gen. 1

13 CENTER FOR BIOLOGICAL SEQUENCE ANALYSIS Genetic drift Gen. 1

14 CENTER FOR BIOLOGICAL SEQUENCE ANALYSIS Genetic drift Gen. 1

15 CENTER FOR BIOLOGICAL SEQUENCE ANALYSIS Genetic drift Gen. 1

16 CENTER FOR BIOLOGICAL SEQUENCE ANALYSIS Genetic drift Gen. 1 Gen. 2

17 CENTER FOR BIOLOGICAL SEQUENCE ANALYSIS Genetic drift Gen. 1 Gen. 2

18 CENTER FOR BIOLOGICAL SEQUENCE ANALYSIS Genetic drift Gen. 1 Gen. 2

19 CENTER FOR BIOLOGICAL SEQUENCE ANALYSIS Genetic drift Gen. 1 Gen. 2 Gen. 3

20 CENTER FOR BIOLOGICAL SEQUENCE ANALYSIS Genetic drift Gen. 1 Gen. 2 Gen. 3

21 CENTER FOR BIOLOGICAL SEQUENCE ANALYSIS Genetic drift Gen. 1 Gen. 2 Gen. 3

22 CENTER FOR BIOLOGICAL SEQUENCE ANALYSIS Genetic drift Gen. 1 Gen. 2 Gen. 3 Gen. 4

23 CENTER FOR BIOLOGICAL SEQUENCE ANALYSIS Genetic drift Alleles will eventually reach a frequency of 0 or 1 Genetic diversity decreases Effect is more strongly felt in small populations

24 CENTER FOR BIOLOGICAL SEQUENCE ANALYSIS Time to fixation and time between fixations

25 CENTER FOR BIOLOGICAL SEQUENCE ANALYSIS Drift and mutation

26 CENTER FOR BIOLOGICAL SEQUENCE ANALYSIS Genetic Drift: The bottleneck effect “Alleles” in original population “Alleles” remaining after bottleneck

27 CENTER FOR BIOLOGICAL SEQUENCE ANALYSIS CheetahBottleneck effect

28 CENTER FOR BIOLOGICAL SEQUENCE ANALYSIS Northern Elephant Seal Reduced to 20 individuals in 1896 Now 30,000 individuals, with no detectable genetic diversity Bottleneck Effect

29 CENTER FOR BIOLOGICAL SEQUENCE ANALYSIS Genetic Drift: The founder effect Change in allele frequencies when a new population arises from only a few individuals. e.g., only a few fish are introduced into a lake. e.g., only a few birds make it to an island.

30 CENTER FOR BIOLOGICAL SEQUENCE ANALYSIS Scorpaenidae Lionfish Pterois volitans Founder Effect New Atlantic population, maybe from only 10 individuals www.fishbase.org

31 CENTER FOR BIOLOGICAL SEQUENCE ANALYSIS Exercise: Genetic drift simulation Starting point: population with N individuals, fraction p has genotype A, fraction (1-p) has genotype aStarting point: population with N individuals, fraction p has genotype A, fraction (1-p) has genotype a All individuals produce 200 offspring of same genotype as parent. (offspring also has fraction p genotype A)All individuals produce 200 offspring of same genotype as parent. (offspring also has fraction p genotype A) Survival rate = 1/200 => Constant population size NSurvival rate = 1/200 => Constant population size N Death strikes randomly: each generation N random individuals surviveDeath strikes randomly: each generation N random individuals survive Investigate drift of allele A frequency:.Investigate drift of allele A frequency:. –Find proportion of populations where A is fixed (p=0.4; N=20, N=80) –Find average time to fixation of A (p=0.4, N=10, 20,...130)

Download ppt "CENTER FOR BIOLOGICAL SEQUENCE ANALYSIS Molecular Evolution Course #27615 Anders Gorm Pedersen Molecular Evolution Group Center for Biological Sequence."

Similar presentations

Evolutionary Change in Populations

Evolutionary Change in Populations
The Five Factors of Evolution

The Five Factors of Evolution
Discover Biology FIFTH EDITION

Discover Biology FIFTH EDITION
Microevolution Chapter 18 contined. Microevolution  Generation to generation  Changes in allele frequencies within a population  Causes: Nonrandom.

Microevolution Chapter 18 contined. Microevolution  Generation to generation  Changes in allele frequencies within a population  Causes: Nonrandom.
Evolution of Populations Chapter 23. Macroevolution Evolution on a large scale Changes in plants & animals Where new forms replace old Major episodes.

Evolution of Populations Chapter 23. Macroevolution Evolution on a large scale Changes in plants & animals Where new forms replace old Major episodes.
14 Molecular Evolution and Population Genetics

14 Molecular Evolution and Population Genetics
CENTER FOR BIOLOGICAL SEQUENCE ANALYSIS Molecular Evolution Course #27615 Anders Gorm Pedersen Molecular Evolution Group Center for Biological Sequence.

CENTER FOR BIOLOGICAL SEQUENCE ANALYSIS Molecular Evolution Course #27615 Anders Gorm Pedersen Molecular Evolution Group Center for Biological Sequence.
KEY CONCEPT A population shares a common gene pool.

KEY CONCEPT A population shares a common gene pool.
Evolution of Populations

Evolution of Populations
PROCESS OF EVOLUTION I (Genetic Context). Since the Time of Darwin  Darwin did not explain how variation originates or passed on  The genetic principles.

PROCESS OF EVOLUTION I (Genetic Context). Since the Time of Darwin  Darwin did not explain how variation originates or passed on  The genetic principles.
Population Genetics Packet #29. Population Genetics The study of genetic variability within the population and of the forces that act on it.

Population Genetics Packet #29. Population Genetics The study of genetic variability within the population and of the forces that act on it.
Allele Frequencies: Changing Chapter 15. Changing Allele Frequencies 1.Mutation – introduces new alleles into population 2.Natural Selection – specific.

Allele Frequencies: Changing Chapter 15. Changing Allele Frequencies 1.Mutation – introduces new alleles into population 2.Natural Selection – specific.
AGENTS THAT CHANGE GENE FREQUENCIES. NATURAL SELECTION  Involves the environment selecting for/against certain phenotypes.

AGENTS THAT CHANGE GENE FREQUENCIES. NATURAL SELECTION  Involves the environment selecting for/against certain phenotypes.
Population Genetics Chapter 15. Red hair will eventually die out because it’s recessive... Brown eyes are dominant so they will take over... Little toes.

Population Genetics Chapter 15. Red hair will eventually die out because it’s recessive... Brown eyes are dominant so they will take over... Little toes.
Evolution of Populations

Evolution of Populations
Genes Within Populations

Genes Within Populations
Natural Selection is the Mechanism of Evolution Objectives: 1.Summarize Darwin’s theory of natural selection. 2.Compare and contrast artificial selection.

Natural Selection is the Mechanism of Evolution Objectives: 1.Summarize Darwin’s theory of natural selection. 2.Compare and contrast artificial selection.
Microevolution How does evolution work?

Microevolution How does evolution work?
KEY CONCEPT Natural selection is not the only mechanism through which populations evolve. Five factors that can lead to evolution.

KEY CONCEPT Natural selection is not the only mechanism through which populations evolve. Five factors that can lead to evolution.
Evolution as Genetic Change and Speciation. A Population’s Gene Pool A gene pool is all the alleles available in all of the individuals in a population.

Evolution as Genetic Change and Speciation. A Population’s Gene Pool A gene pool is all the alleles available in all of the individuals in a population.

Similar presentations

Ads by Google