Estimating Risk of Inherited Genetic Disease COPY

Question 1

What is meant by fitness?

Answer 1

The relative ability of organisms to survive and pass on genes

Question 2

What is an allele that increases fitness?

Answer 2

Advantageous allele

Question 3

What is a neutral allele?

Answer 3

Doesn’t effect fitness

Question 4

What is a deleterios allele?

Answer 4

A decrease in fitness - causes disease

Question 5

What affects the health of the population?

Answer 5

The frequency of alleles

Question 6

Do dominant alleles become more common from generation to generation?

Answer 6

No, relative frequencies remain constant

genotype frequencies also remain constant

dominant alleles dont become more common at the expense of recessive ones

Question 7

What are the assumptions underlying the HWE?

Answer 7

IDEAL POPULATION

• Mutation can be ignored
• Migration is negligible (No gene flow)
• Mating is random
• No selective pressure
• Population size is large
• Allele frequencies are equal in the sexes

Question 8

What does the introduction of new alleles as a result of migration or intermarriage leads to?

Answer 8

New gene frequency in hybrid population.

Question 9

What is the result of non-random mating?

Answer 9

Leads to increase mutant alleles, thereby increasing proportion of affected homozygotes

Question 10

What is the choosing of partners due to shared characteristics?

Answer 10

Assortative Mating

Question 11

What is Consanguinity

Answer 11

Marriage between close blood relatives.

Question 12

What is natural selection?

Answer 12

A gradual process by which biological traits become either more or less common in a population.

Question 13

What is Negative selection?

Answer 13

• Reduces reproductive fitness.
• decreases the prevalence of traits.
• leads to gradual reduction of mutant allele

Question 14

What is positive selection?

Answer 14

• Increases reproductive fitness.
• Increases the prevalence of adaptive traits.
• Heterozygote advantage.

Question 15

What is the effect of small population?

Answer 15

Can exhibit “genetic drift” and cause “founder effect”.

Question 16

What is meant by genetic drift?

Answer 16

Random fluctuation of one allele transmitted to high proportion of offspring by chance.
mutations are widespread and neutral, statistical drift of gene frequencies due to chance or random events rather than natural selection in the formation of successive generations

Question 17

What is the founder effect?

Answer 17

The reduction in genetic variation that results when a small subset of a large population is used to establish a new colony.

Question 18

What is the bottleneck effect?

Answer 18

Catastrophe results in a population with a high expression of a certain phenotype, regardless of wether or not it is advantageous to the population

Question 19

recessive mutation and disease

Answer 19

• mutation in recessive genes rarely affects carriers
• where it does it is often associated with a selective pressure
• de novo recessive mutation is uncommon as a cause of disease

Question 20

dominant mutation

Answer 20

de novo mutation is common in dominant disorders

up to 1/3 of lethal X-L cases are due to a de novo mutation

Question 21

applications of HWE

Answer 21

• calculating risk in genetic counselling

- planning population based carrier screening programmes