Population genetics

Question 1

What is the gene pool?

Answer 1

the total information from all the genes and alleles of breeding individuals in a population at a particular time

Question 2

What is the allele frequency?

Answer 2

the proportion of organisms in the population carrying a particular allele

Question 3

What does it mean about the population if there is a change in allele frequency?

Answer 3

the population is evolving

Question 4

In larger populations, allele frequencies remain…

Answer 4

generally stable

Question 5

What are the two equations for the Hardy-Weinberg principle?

Answer 5

p + q = 1
p^2 + 2pq + q^2 = 1

Question 6

What does this equation relate to p + q = 1?

Answer 6

alleles of one gene, p = dominant allele frequency, q = recessive allele frequency

Question 7

What does this equation relate to p^2 + 2pq + q^2 = 1?

Answer 7

individuals in a population, p^2 = frequency of homozygous dominant, 2pq = frequency of heterozygous, q^2 = frequency of homozygous recessive

Question 8

What does the Hardy-Weinberg principle assume?

Answer 8

that the population is:
-large
-has random mating
-is experiencing no selection
-has no mutation or migration

Question 9

What is disruptive selection?

Answer 9

selection pressure towards the extremes that creates two modal values

Question 10

What does disruptive selection cause?

Answer 10

sympatric speciation

Question 11

What are forces of evolutionary change?

Answer 11

natural selection, genetic drift

Question 12

What is genetic drift?

Answer 12

a change in allele frequency due to chance rather than selection

Question 13

What does genetic drift have a bigger impact on?

Answer 13

smaller populations

Question 14

Use the example of a bird and green/brown bugs to explain the difference between natural selection and genetic drift

Answer 14

-natural selection - a bird is more likely to see the green bug over a brown one
-genetic drift - a random green beetle is stood on

Question 15

When does natural selection occur?

Answer 15

when alleles that enhance the fitness of the individuals that carry them rise in frequency

Question 16

What can cause genetic variation?

Answer 16

-mutation
-independent segregation
-crossing over
-random fertilisation of gametes

Question 17

What causes interspecific variation?

Answer 17

-differences in DNA
-structure and sequence of genes
-the way in which genes are expressed

Question 18

What can cause intraspecific variation?

Answer 18

a combination of both environmental and genetic factors, and epigenetics

Question 19

What are the two types of variation?

Answer 19

discontinuous and continuous

Question 20

What is discontinuous variation?

Answer 20

limited to a fixed number of traits, such as blood group - a few genes with multiple alleles. the environment usually has a lesser effect

Question 21

What is continuous variation?

Answer 21

controlled by many genes, environment has a significant effect, and is more likely to be a number like weight

Question 22

How can we make a sample more representative?

Answer 22

-increase study size
-reduce sampling bias by random sampling

Question 23

What can be used to determine the relative importance of the environment and genes?

Answer 23

twin studies - identical vs non-identical

Question 24

What happens if a species becomes isolated from the other populations?

Answer 24

-there will be no gene flow between the isolated population and the others
-this may lead to the accumulation of genetic differences
-leading to the isolated population being unable to breed and produce fertile offspring with organisms from the other population
-this reproductive isolation means that a new species has evolved

Question 25

What is speciation?

Answer 25

an evolutionary process that results in the formation of a new species from a pre-existing species

Question 26

What are the two ways in which speciation can occur?

Answer 26

allopatric and sympatric

Question 27

What is isolation?

Answer 27

when two populations are separated, leading to no gene flow

Question 28

What is allopatric speciation?

Answer 28

-occurs when a geographical barrier physically isolates populations of a species
-the two populations begin to evolve separately as a result of a random mutation, genetic drift, and natural selection
-eventually the two populations reach a degree of genetic difference where they can no longer interbreed to produce fertile offspring

Question 29

What is sympatric speciation?

Answer 29

-divergence of species within the same geographical location
-may be due to genetic abnormalities/differences
-prevents interbreeding between those species to produce fertile offspring