8/26/14 - Genetic Variation in Individuals & Populations

Question 1

What is the founder effect?

Answer 1

When a small subpopulation with a different allele distribution breaks away from the general population

Question 2

What is aneuploidy?

Answer 2

An abnormal number of chromosomes.

Question 2

Why are point mutations often paternally inherited?

Answer 2

Since spermatogonium undergo repeated mitotic division, they are more prone to replication errors, the most common being point mutations.

Question 3

What diseases are typically associated with MHC molecules?

Answer 3

Autoimmune

Question 3

What is a classic case of a balanced polymorphism?

Answer 3

Sick cell heterozygosity confering resistance to malaria.

Question 4

An autosomal recessive disease is found in 2% of the population. Calculate the percentage of disease carriers in the same population. (draw)

Answer 4

Heterozygote carriers: 24%

Question 5

What is a haplotype?

Answer 5

A cluster of linked genes. Due to their close proximity, linked genes are almost always inherited together.

Question 6

What germline mutations are more likely to occur in women?

Answer 6

Frequency of nondisjunction causing trisomies and large deletions increases with age.

Question 7

What are the characteristics of the A and B blood types?

Answer 7

Dominant

Question 9

What is the difference between a point mutation and a SNP?

Answer 9

SNP is a polymorphism, which means it has to be present in >1% of the population.

Question 9

If a disease confers 40% fitness, what percentage of individuals in that population are able to procreate?

Answer 9

40%

Question 10

What is a copy number polymorphism?

Answer 10

An abnormal number of gene copies.

Question 11

What five main factors affect the rate of germline mutation development?

Answer 11

Gene size Presence of CG sequences Mutation phenotype Parental age Parental gender

Question 12

What is a balanced polymorphism?

Answer 12

Forces exist to both remove and maintain polymorphisms from a population, favoring the heterozygote form.

Question 13

What germline mutations are more likely to occur in men?

Answer 13

Point mutations

Question 14

What is a VNTR?

Answer 14

Variable number tandem repeats

Question 14

What are the characteristics of the AB blood type?

Answer 14

Co-dominant, universal recipient

Question 15

What are the characteristics of MHC I molecules?

Answer 15

MHC I molecules are expressed on all nucleated cells and residue on cell surfaces. They present protein fragments from within the cell - called epitopes - to immune cells. If the immune cells recognize these epitopes, they will initiate an immune response against that cell.

Question 15

What is gene flow?

Answer 15

Process by which genes diffuse in a foreign population over time.

Question 16

What is genetic drift?

Answer 16

Changes with the environment favoring a genetically defined subpopulation

Question 17

Why are large chromosome deletions more often maternally inherited?

Answer 17

Large deletions more likely due to unequal crossing over during oocyte development.

Question 18

What is fitness?

Answer 18

The ability to procreate

Question 20

Why are most people Rh+?

Answer 20

Resus factor expression (Rh+) is a dominant trait, so an individual will need two Rh- alleles to be Rh-.

Question 21

Hardy-Weinberg equilibrium for 2 alleles (3 genotypes)

Answer 21

Frequency = P^2 + 2PQ + Q^2

Question 23

What are the characteristics of MHC II molecules?

Answer 23

MHC II molecules are usually expressed on professional antigen-presenting cells (APCs), such as macrophages. If a macrophage consumes a bacterium, it will degrade its proteins and express bacterial protein fragments bound the MHC II molecules on its cell surface, triggering an immune response when an immune cell binds.

Question 24

What are the characteristics of the O blood type?

Answer 24

Recessive, universal donor

Question 25

What type of mutation results in a single base pair substitution?

Answer 25

Point mutation (not confused with SNP)

Question 27

What is the main function of MHCs?

Answer 27

To present antigens to immune cells.

Question 29

What happens when fitness = 0?

Answer 29

The disorder is lethal, and selection removes those mutant alleles in a single generation.

Question 30

If a disease confers low fitness, how is that disease maintained in a population?

Answer 30

De novo mutations

Question 31

What is translocation?

Answer 31

A chromosomal rearrangement whereby a segment of one chromosome is moved to a different region.

Question 32

Calculate the probability of each genotype given the frequency of two alleles: P (0.7), Q (0.3) (draw)

Answer 32

PP: 0.49, 49% PQ: 0.42, 42% QQ: 0.09, 9%

Question 33

What are the four conditions that must be met for the Hardy-Weinberg equilibrium?

Answer 33

Large population Random mating No mutations No selection

Question 34

What process demands strict MHC matching?

Answer 34

Organ transplantation