Population Genetics & Epigenetics

Question 1

Process of Natural selection

Answer 1

-Natural variation in a population
-some invidivudals have beneficial characteristics
-so they are better able to cope with the selection pressures in their habitat
-they have a selective advantage
-more likely to reach reproductive age to pass on advantageous allele to offspring
-Continues over several generations & frequency of advantageous allele increases
-Leads to natural selection
-Principle of survival of the fittest

Question 2

gene pool definition

Answer 2

-all variants in a population together

Question 3

Genetic bottleneck

Answer 3

-Event resulting in a drastic reduction in population numbers
-eg. due to natural disaster
-decreases genetic diversity

Question 4

Founder effect

Answer 4

-specific type of genetic bottleneck
-small group of individuals break away, forms new colony
-will lead to a difference in allele frequency

Question 5

species definition

Answer 5

group of individuals which can interbreed together to produce fertile offfspring

-problems:
can’t be used to classify organisms which don’t produce sexually

Question 6

Speciation

Answer 6

-population becomes separated
-individuals within each sub-population show variation
-different habitats have different selection pressures
-Some individuals have beneficial characteristics
-Natural selection occurs
-After many generations, new individuals in each population cannot interbreed to produce fertile offspring

Question 7

What are the 2 isolation mechanisms

Answer 7

Geographical isolation
-involves a physical barrier which causes 2 groups to experience different selection pressues

Reproductive isolation
-Physical mating is not possible
-Temporal, behavioural and anatomical barriers

Question 8

epigenetic changes

Answer 8

structure of the gene remains unaltered but genes are switched on or off by epigenetic changes

Question 9

what is the purpose of epigenetic changes?

Answer 9

allows expression of only the genes required for functioning

Question 10

describe 2 mechanisms of epigenetic changes

Answer 10

DNA methylation
-methyl groups added to DNA
-decreased transcription
-decreased gene expression

Histone modification
-Histones order & package DNA
-adds acetyl/methyl/phosphate group to histone protein
-makes gene more/less accessible to transcription
-So activates/ deactivates gene

Question 11

Hardy Weinberg assumptions

Answer 11

-large population
-random mating
-no new mutations
-no migration in or out
-no selection

Question 12

Hardy Weinburg equations

Answer 12

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

p frequency dominant allele
q frequency recessive allele
p2 frequency homozygous dominant
q2 frequency homozygous recessive
pq frequency heterozygous