Population Genetics. Hardy-Weinberg Equilibrium Determination a)A b)B c)both A and B d)neither A nor...

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Transcript of Population Genetics. Hardy-Weinberg Equilibrium Determination a)A b)B c)both A and B d)neither A nor...

Page 1: Population Genetics. Hardy-Weinberg Equilibrium Determination a)A b)B c)both A and B d)neither A nor B Which of these populations are in Hardy- Weinberg.

Population Genetics

Page 2: Population Genetics. Hardy-Weinberg Equilibrium Determination a)A b)B c)both A and B d)neither A nor B Which of these populations are in Hardy- Weinberg.

Hardy-Weinberg Equilibrium Determination

a) A

b) B

c) both A and B

d) neither A nor B

Which of these populations are in Hardy-Weinberg equilibrium?

Page 3: Population Genetics. Hardy-Weinberg Equilibrium Determination a)A b)B c)both A and B d)neither A nor B Which of these populations are in Hardy- Weinberg.

Question 6 – Chap. 23

• Researchers examining a particular gene in a fruit fly population discovered that the gene can have either of two slightly different sequences, designated A1 and A2. Further tests showed that 70% of the gametes produced in the population contained the A1 sequence. If the population is at Hardy-Weinberg equilibrium, what proportion of flies carries both A1 and A2?

• A 0.7 B 0.49 C 0.21 D 0.42 E 0.09

Page 4: Population Genetics. Hardy-Weinberg Equilibrium Determination a)A b)B c)both A and B d)neither A nor B Which of these populations are in Hardy- Weinberg.

Question from an earlier edition of Campbell

• At a locus with a dominant and recessive allele in Hardy-Weinberg equilibrium, 16% of the individuals are homozygous for the recessive allele. What is the frequency of the dominant allele in the population?

• A 0.84 B 0.36 C 0.6 D 0.4 E 0.48

Page 5: Population Genetics. Hardy-Weinberg Equilibrium Determination a)A b)B c)both A and B d)neither A nor B Which of these populations are in Hardy- Weinberg.

Hardy-Weinberg Equilibrium

Hardy-Weinberg Equilibrium is based on:

1. A very large population where all genotypes are equally viable

2. Random mating (panmixia)

3. No mutations

4. No gene flow (dispersal of individuals and their genes)

5. No natural selection

Page 6: Population Genetics. Hardy-Weinberg Equilibrium Determination a)A b)B c)both A and B d)neither A nor B Which of these populations are in Hardy- Weinberg.

Evolutionary Change

• Evolution is a generation to generation change in a population’s frequencies of alleles – change in proportions of alleles in the gene pool is evolution at its smallest scale and is often referred to as microevolution

• The two main causes of microevolution are genetic drift and natural selection

Page 7: Population Genetics. Hardy-Weinberg Equilibrium Determination a)A b)B c)both A and B d)neither A nor B Which of these populations are in Hardy- Weinberg.

Natural Selection

Page 8: Population Genetics. Hardy-Weinberg Equilibrium Determination a)A b)B c)both A and B d)neither A nor B Which of these populations are in Hardy- Weinberg.

Genetic Drift

• Random changes in gene frequency in a population – this can lead to losses in genetic diversity – the population becomes more homozygous

• this is most important in small populations

Page 9: Population Genetics. Hardy-Weinberg Equilibrium Determination a)A b)B c)both A and B d)neither A nor B Which of these populations are in Hardy- Weinberg.

Genetic Drift

Generation 1p (frequency of CR) = 0.7 q (frequency of CW) = 0.3

CRCR CRCR

CRCW

CWCW CRCR

CRCW

CRCR CRCW

CRCR CRCW

Page 10: Population Genetics. Hardy-Weinberg Equilibrium Determination a)A b)B c)both A and B d)neither A nor B Which of these populations are in Hardy- Weinberg.

Genetic Drift

5plantsleaveoff-

spring

Generation 1p (frequency of CR) = 0.7 q (frequency of CW) = 0.3

CRCR CRCR

CRCW

CWCW CRCR

CRCW

CRCR CRCW

CRCR CRCW

CRCRCWCW

CRCW

CRCR CWCW

CRCW

CWCW CRCR

CRCW CRCW

Generation 2p = 0.5 q = 0.5

Page 11: Population Genetics. Hardy-Weinberg Equilibrium Determination a)A b)B c)both A and B d)neither A nor B Which of these populations are in Hardy- Weinberg.

Genetic Drift

5plantsleaveoff-

spring

Generation 1p (frequency of CR) = 0.7 q (frequency of CW) = 0.3

CRCR CRCR

CRCW

CWCW CRCR

CRCW

CRCR CRCW

CRCR CRCW

CRCRCWCW

CRCW

CRCR CWCW

CRCW

CWCW CRCR

CRCW CRCW

Generation 2p = 0.5 q = 0.5

2plantsleaveoff-

spring

CRCR

CRCR CRCR

CRCRCRCR

CRCR CRCR

CRCR

CRCR CRCR

Generation 3p = 1.0 q = 0.0

Page 12: Population Genetics. Hardy-Weinberg Equilibrium Determination a)A b)B c)both A and B d)neither A nor B Which of these populations are in Hardy- Weinberg.

Population Bottleneck

Page 13: Population Genetics. Hardy-Weinberg Equilibrium Determination a)A b)B c)both A and B d)neither A nor B Which of these populations are in Hardy- Weinberg.

Originalpopulation

Page 14: Population Genetics. Hardy-Weinberg Equilibrium Determination a)A b)B c)both A and B d)neither A nor B Which of these populations are in Hardy- Weinberg.

Originalpopulation

Bottleneckingevent

Page 15: Population Genetics. Hardy-Weinberg Equilibrium Determination a)A b)B c)both A and B d)neither A nor B Which of these populations are in Hardy- Weinberg.

Originalpopulation

Bottleneckingevent

Survivingpopulation

Page 16: Population Genetics. Hardy-Weinberg Equilibrium Determination a)A b)B c)both A and B d)neither A nor B Which of these populations are in Hardy- Weinberg.

Northern Elephant Seal

Page 17: Population Genetics. Hardy-Weinberg Equilibrium Determination a)A b)B c)both A and B d)neither A nor B Which of these populations are in Hardy- Weinberg.

Northern Elephant Seal Population

Page 18: Population Genetics. Hardy-Weinberg Equilibrium Determination a)A b)B c)both A and B d)neither A nor B Which of these populations are in Hardy- Weinberg.

Pre-bottleneck(Illinois, 1820)

Post-bottleneck(Illinois, 1993)

Greater prairie chicken

Range of greater prairie chicken

(a)

Location Population size

Number of alleles per locus

Percentage of eggs hatched

93<50

5.23.7

5.8

5.8

99

96

1,000–25,000 <50

750,000

75,000–200,000

Nebraska, 1998 (no bottleneck)

(b)

Kansas, 1998 (no bottleneck)

Illinois 1930–1960s 1993

Page 19: Population Genetics. Hardy-Weinberg Equilibrium Determination a)A b)B c)both A and B d)neither A nor B Which of these populations are in Hardy- Weinberg.

Pre-bottleneck(Illinois, 1820)

Post-bottleneck(Illinois, 1993)

Greater prairie chicken

Range of greater prairie chicken

(a)

Page 20: Population Genetics. Hardy-Weinberg Equilibrium Determination a)A b)B c)both A and B d)neither A nor B Which of these populations are in Hardy- Weinberg.

Location Population size

Number of alleles per locus

Percentage of eggs hatched

93<50

5.23.7

5.8

5.8

99

96

1,000–25,000 <50

750,000

75,000–200,000

Nebraska, 1998 (no bottleneck)

(b)

Kansas, 1998 (no bottleneck)

Illinois 1930–1960s 1993

Page 21: Population Genetics. Hardy-Weinberg Equilibrium Determination a)A b)B c)both A and B d)neither A nor B Which of these populations are in Hardy- Weinberg.

Founder effect – founder population and three possible new populations

Page 22: Population Genetics. Hardy-Weinberg Equilibrium Determination a)A b)B c)both A and B d)neither A nor B Which of these populations are in Hardy- Weinberg.

Mal de Meleda – founder effect

Page 23: Population Genetics. Hardy-Weinberg Equilibrium Determination a)A b)B c)both A and B d)neither A nor B Which of these populations are in Hardy- Weinberg.

Serial Founder Effect

• Serial founder effects have occurred when populations migrate over long distances. Such long distance migrations typically involve relatively rapid movements followed by periods of settlement. The populations in each migration carry only a subset of the genetic diversity carried from previous migrations. As a result, genetic differentiation tends to increase with geographic distance.

Page 24: Population Genetics. Hardy-Weinberg Equilibrium Determination a)A b)B c)both A and B d)neither A nor B Which of these populations are in Hardy- Weinberg.

Movement of mitochondrial genes out of Africa

Page 25: Population Genetics. Hardy-Weinberg Equilibrium Determination a)A b)B c)both A and B d)neither A nor B Which of these populations are in Hardy- Weinberg.

‘Wisteria vine’ model of human genetic diversity

Page 26: Population Genetics. Hardy-Weinberg Equilibrium Determination a)A b)B c)both A and B d)neither A nor B Which of these populations are in Hardy- Weinberg.

Gene Flow

• Gene flow is the movement of alleles in and out of a population

• Gene flow occurs because gametes or fertile individuals move from one population to another and take their genes with them

Page 27: Population Genetics. Hardy-Weinberg Equilibrium Determination a)A b)B c)both A and B d)neither A nor B Which of these populations are in Hardy- Weinberg.

Gene flow

Page 28: Population Genetics. Hardy-Weinberg Equilibrium Determination a)A b)B c)both A and B d)neither A nor B Which of these populations are in Hardy- Weinberg.

Gene Flow in Conifers

Page 29: Population Genetics. Hardy-Weinberg Equilibrium Determination a)A b)B c)both A and B d)neither A nor B Which of these populations are in Hardy- Weinberg.

Population in which the surviving females eventually bred

Central

Eastern

Su

rviv

al r

ate

(%)

Females born in central population

Females born in eastern population

Parus major

60

50

40

30

20

10

0

Central population

NORTH SEA Eastern population

Vlieland, the Netherlands

2 km

Page 30: Population Genetics. Hardy-Weinberg Equilibrium Determination a)A b)B c)both A and B d)neither A nor B Which of these populations are in Hardy- Weinberg.

Non-Random Mating

• Hardy-Weinberg assumes random mating – if mating is not random then the population may change in the short term – the most common form of non-random mating is in-breeding – the mating of closely related individuals

• In fact inbreeding is very common – many mammals probably mate with first or second cousins in the wild; many plants self-pollinate – the ultimate form of inbreeding

• Inbreeding tends to produce homozygous populations

Page 31: Population Genetics. Hardy-Weinberg Equilibrium Determination a)A b)B c)both A and B d)neither A nor B Which of these populations are in Hardy- Weinberg.

Inbreeding and White Squirrels

Page 32: Population Genetics. Hardy-Weinberg Equilibrium Determination a)A b)B c)both A and B d)neither A nor B Which of these populations are in Hardy- Weinberg.

Mutations

• Mutations are the ultimate source of new genetic variations – a new mutation that is transmitted in gametes immediately changes the gene pool of a population by inserting a new allele into the gene pool

Page 33: Population Genetics. Hardy-Weinberg Equilibrium Determination a)A b)B c)both A and B d)neither A nor B Which of these populations are in Hardy- Weinberg.
Page 34: Population Genetics. Hardy-Weinberg Equilibrium Determination a)A b)B c)both A and B d)neither A nor B Which of these populations are in Hardy- Weinberg.