Population genetics

Question 1

define evolution:

Answer 1

• change of allele frequencies over time

Question 2

what causes change to allele frequencies:

Answer 2

• natural selection

- genetic drift

Question 3

natural selection:

Answer 3

• organisms best suited to environment have more resources for survival and reproduction

Question 4

fitness:

Answer 4

• relative genetic contribution of individual to next generation
• successful alleles individuals carry passed on

Question 5

adaptation:

Answer 5

• change in populations through natural selection

Question 6

directional selection:

Answer 6

• individuals with traits at one extreme favoured over another

Question 7

stabilising selection:

Answer 7

• individual with intermediate traits favoured

Question 8

disruptive selection:

Answer 8

• individuals from either extreme favoured

Question 9

eg. directional selection

Answer 9

• herbicide application
• many plant species evolving with resistance
• also antibiotic resistance in hopsitals

Question 10

genetic drift:

Answer 10

• change in allele frequencies across generations due to chance events

Question 11

list chance events:

Answer 11

• random disturbances
• small populations
• Founder effects

Question 12

population size:

Answer 12

• genetic drift more likely to occur in small populations
  = fixation of allele and loss of others
• less likely in large populations, random events are buffered

Question 13

Founder effect:

Answer 13

• individuals disperse to new area, subset of alleles from entire population
• large change in allele frequencies
• inbreeding

Question 14

bottleneck effect:

Answer 14

• rapid decrease in population size due to disturbance or natural disaster
• removes individuals with some alleles from population
• those which survive alter gene frequencies

Question 15

eg. Pingelap

Answer 15

• island of colourblind
• 10% individuals completely colourblind in population
• 1775 population reduced to 20 people due to typhoon
• bottleneck effect
• all colourblind people can be traced back to one person with recessive genetic disorder

Question 16

significance of Pingelap:

Answer 16

• random disturbance initially changed allele frequencies
• bottleneck left small founding population
• random chance + small population size + inbreeding = allele not adaptive have high frequency in population

Question 17

gene flow:

Answer 17

• allele moves btw populations
• can increase genetic variation
• decrease effects of genetic drift
• can lead to homogenisation across populations
• dilute effects of localised natural selection and adaptation

Question 18

population:

Answer 18

• individuals of species which interbreed with each other but not w individuals of same species of another population
• different populations becomes more genetically differentiated
• over long periods of time, no genetic exchange will evolve into different species

Question 19

gene pool:

Answer 19

• entire genetic content of population
• every allele
• we only study specific alleles

Question 20

mutations:

Answer 20

• change in DNA sequence
• error in DNA replication
• caused by mutagens
• most mutations are deleterious, but some create alleles that increase fitness

Question 21

sexual reproduction:

Answer 21

• new combinations of alleles produced

- recombination of alleles in meiosis

Question 22

Hardy-Weinberg equilibrium:

Answer 22

• when allele and genotype frequencies remain constant from gen to gen, population is not evolving
• only Mendelian segregation and recombination of alleles at work
• this type of population: Hardy-Weinberg equilibrium

Question 23

how to determine offsprings in Hardy-Weinberg equilibrium:

Answer 23

• consider combo of alleles in all crosses in population (genotype and allele frequencies)
• will add up to 1 (100%)

Question 24

Hardy-Weinburg equilibrium: equation

Answer 24

• at locus with 2 alleles
• 3 genotypes will appear:

p2 + 2pq + q2 = 1

Question 25

result of not meeting 1 of 5 conditions of Hardy-Weinberg equilibrium:

Answer 25

1. no mutations
2. random mating
3. no natural selection
4. extremely large population size
5. no gene flow

• allele and genotype frequency will change
• real populations change over time

Question 26

evolution:

Answer 26

• change in allele frequencies btw generations

Question 27

to calculate genotype frequency:

Answer 27

no. of individuals with specific genotype ÷ no. of total individuals

Question 28

to calculate allele frequency:

Answer 28

no. of particular allele ÷ total no. of alleles in all individuals

Question 29

how many genotypes per individual?

Answer 29

one

Question 30

how many alleles per individual?

Answer 30

two

- one per chromosome of every individual