Population Genetics

Question 1

What is the study of population genetics?

Answer 1

The study of variation in allele and genotype frequencies within a population

Question 2

What does it mean is genes are polymorphic?

Answer 2

they will occur in a number of different forms/ alleles - multiple versions of them exist (i.e: hair colour, eye colour)

Question 3

What is the gene pool

Answer 3

the collection of all the alleles of all the genes found within a freely interbreeding population

Question 4

Why does Hardy-Weinberg Equilibrium rarely apply to population genetics?

Answer 4

Because it is a null model. It can only be applied if the following are NOT active:

• Mutations
• Sexual selection
• Genetic drift/ gene flow

Question 5

What is recombination?

Answer 5

the process whereby a cell generates new chromosomal combinations, compared with that cell or with those of its progenitors

Question 6

Does recombination create new diversity?

Answer 6

No - it generates new combinations of existing diversity, creating more VARIATION

Question 7

What letter represents the effective population?

Answer 7

Ne

Question 8

What does ‘Ne’ describe?

Answer 8

The effective population size - shows the same rate of loss of genetic variation due to genetic drift as for the population of interest

Question 9

Name 3 consequences of a decreasing population size?

Answer 9

Inbreeding
Genetic drift
Homozygosity
Subpopulation differentiation

Question 10

Why is Ne generally less than N?

Answer 10

population sizes vary from generation to generation
Unequal sex ratios
Overlapping generations
Geographical dispersion of populations

Question 11

What is gene flow

Answer 11

the introduction of genetic material (by interbreeding) from one population of a species to another, thereby changing the composition of the gene pool of the receiving population

Question 12

Why is gene flow good for populations?

Answer 12

The introduction of new alleles through gene flow increases variability within the population and makes possible new combinations of traits

Question 13

What are two ways for gene flow?

Answer 13

Immigration

Emigration

Question 14

Which letter represents the movement of individuals

Answer 14

f

Question 15

What is genetic drift?

Answer 15

the change in the frequency of an existing gene variant (allele) in a population due to random sampling of organisms
- as a results of random fluctuations in the transfer of alleles from one generation to the next

Question 16

What is the difference between genetic drift and gene flow?

Answer 16

Genetic drift = changes in gene frequencies from one generation to the next
Gene flow = variation in gene frequencies from one population to another

Question 17

Which two effects can cause genetic drift?

Answer 17

Bottle necking

Founder effect

Question 18

What is the bottle neck effect

Answer 18

When adverse environmental conditions reduce the genetic variation in a population

Question 19

What is the founder effect?

Answer 19

The loss of genetic variation due to geographical separation of a subset of the population

Question 20

Give an example of bottle necking

Answer 20

Northern Elephant Seals in the 1890s - hunting reduced population size and subsequently genetic variation

Question 21

What are mutations

Answer 21

changes in the DNA sequence caused by the insertion, deletion or point mutation

Question 22

what is inbreeding and outbreeding

Answer 22

Inbreeding = mating with relatives - causes homozygosity

Outbreeding = mating with non-relatives - increases heterozygosity

Question 23

how do you calculate the inbreeding coefficient

Answer 23

F = (expected no. heterozygotes under random mating - actual freq. of heterozygotes) / expected no. heterozygotes

Question 24

what are darwin’s 3 basic conclusions

Answer 24

Organisms produced more offspring than can survive
Living things are locked in a struggle for survival
Individuals of the same species are rarely identical (they show variation)

Question 25

Name 3 examples of behavioural adaptations

Answer 25

Mating calls
Co-operative hunting
Tool use

Question 26

Name 3 examples of physical (structural) adaptations

Answer 26

Talons
Beaks
Fur
Colouration (camouflage)
Long necks in giraffes

Question 27

Name 3 examples of physiological adaptations

Answer 27

Fat storage in camel humps
Venom/ poison
Hibernation
Metabolic changes

Question 28

name 2 modern examples of natural selection

Answer 28

• Use of antibiotics are leading to resistant bacteria – ‘superbugs’
• Rats have a modified enzyme that allows blood to clot even in the presence of Warfarin

Question 29

define selection pressure

Answer 29

the severity of an organisms circumstances on survival

Question 30

if the selection pressure is greater, what happens to the rate of evolution?

Answer 30

it increases

Question 31

what are the 3 types of selection

Answer 31

stabilising
disruptive
directional

Question 32

which is the most common type of selection

Answer 32

directional

Question 33

describe directional selection

Answer 33

When organisms with a particular phenotype have an advantage and survive to reproduce

Question 34

Describe stabilising selection

Answer 34

in a favourable/unchanging environment selection can lead to standardisation of organisms by selecting against extremes

Question 35

Describe disruptive selection

Answer 35

Where only organisms with extreme phenotypes are selected - phenotypes selected AWAY from the norm

Question 36

What is speciation

Answer 36

The formation of a new species

Question 37

when does speciation occur?

Answer 37

When parts of populations get isolated, experience different environmental conditions