Genetics 5: Population genetics

Question 1

What is the ultimate source of genetic variation

Answer 1

The creation of new allele through mutation, gene duplication or other processes.

Question 2

What is a mutation and their frequency of mutations in exons vs introns

Answer 2

Mutation: A change in organisms DNA that is random (but there are some hotspots).
In exons they are relatively rare- (high fidelity of DNA replication) and mostly silent, but in introns more frequent.

Question 3

Compare somatic vs germline mutations

Answer 3

Germline mutation immediately changes the gene pool of a population by creating a new allele–> transmitted to progeny whereas Somatic is not transmitted to progeny.

Question 4

What is the definition of a Human genetic disorders/hereditary disease

Answer 4

genetic disorders that result from mutations in genes that produce adverse phenotypic effect.

Question 5

What is the genetic basis for Sickle Cell disease that results in the phenotype

Answer 5

The substitution of a single amino acid in the haemoglobin protein of RBCs (glutamate-> valine). This causes sickle cell haemoglobin protein to aggregate into long fibres which deform RBC when Oxygen is low and makes them block small blood vessels.

Question 6

What are the symptoms of Sickle cell disease

Answer 6

Sickle cells block small blood vessels causing physical weakness, pain, organ damage and even paralysis

Question 7

What form of dominance does sickle cell disease people have and what is the common genotype held by sufferers

Answer 7

Codominance so heterozygotes are individuals who have the symptoms, homozygous have fill disease.

Question 8

What is the population

Answer 8

A group of individuals of the same species that live in the same are and interbreed

Question 9

What is a gene pool

Answer 9

The sum of all the alleles of all genes of all individuals in the population

Question 10

What is Hardy Weinberg equilibrium

Answer 10

This is when allele and genotype frequencies will remain constant from one generation to the next in a non-evolving population

Question 11

What is the Hardy Weinberg equations and what is used for

Answer 11

P^2 + 2Pq + q^2 = 1
P + q = 1
They are used to calculate the expected genotype frequencies for the next generation given the observed allele frequencies

Question 12

What is p and q in the hardy weinburg equation and how do you find them

Answer 12

P= frequency of dominant allele (%)
q= frequency of recessive allele (%)
These are counted from counting the # of alleles out of the total number of alleles in the population (% decimal),
Heterozygous counts as 2, homozygous as 1.

Question 13

What are the 5 conditions of the Hardy Weinburg

Answer 13

1. No mutations (no modification to allele frequencies in gene pool)
2. Mating occurs at random
3. No natural selection
   (could lead to skewed values)
4. Extremely large population size (less likely fluctuations in allele frequency)
5. No gene flow (movement of alleles in and out)

Question 14

Compare the variation produced at different types of non random mating

Answer 14

Outbreeding promotes variability while
Inbreeding results in loss of variation and increased homozygosity due to increased likelihood to produce homozygous recessive traits.
Self fertilisation is the fastest way to lose variation

Question 15

What is Genetic Drift

Answer 15

The change in allele frequency as a result of chance events.
This leads to loss of genetic variation (esp rare alleles)

Question 16

Compare founder effect to population bottlenecks

Answer 16

Founder effect is when by chance a smaller population that branches off doesn’t have all the alleles present in the larger population
Whereas
Population bottleneck is when a population is drastically reduced leading to a chance loss or fixation of alleles

Question 17

What is Gene flow and what is its effect on variation

Answer 17

The movement of alleles in or out of a population due to movement of individuals or their gametes.
Tends to reduce differences between populations and therefore homogenise allele frequencies between populations, thus maintaining variation within populations.