Estimating risk of inherited genetic disease

Question 1

Fitness

Answer 1

Relative ability of organisms to survive and pass on genes

Question 2

What does fitness depend on?

Answer 2

Types of alleles eg neutral, deleterious or advantageous

Question 3

Do deleterious mutations sometimes or rarely decrease fitness?

Answer 3

Sometimes

Question 4

Do advantageous mutations sometimes or rarely increase fitness

Answer 4

Rarely

Question 5

Frequency of alleles affect healthy population

Answer 5

Population genetics

Question 6

1 gene with 2 alleles what are p and q

Answer 6

p = dominant q = recessive

Question 7

Genotype frequency

Answer 7

GG/total

Question 8

Allele frequency

Answer 8

Gt/ total alleles ( NB double the number as alleles separate)

Question 9

Do dominant conditions become more common at the expense or recessive alleles?

Answer 9

NO

Question 10

Hardy-Weinberg principle

Answer 10

Use quadratics

Question 11

What are constant generation to generation?

Answer 11

Allele frequency and relative proportion of genotype frequency

Question 12

p squared = q squared = 2pq=

Answer 12

1

Question 13

What can HWE allow?

Answer 13

Calculate risk in genetic counselling

Plan population based carrier screening programmes

Question 14

p squared

Answer 14

Homozygous dominant

Question 15

q squared

Answer 15

Homozygous recessive

Question 16

pq

Answer 16

Heterozygous

Question 17

When is HWE not always achieved?

Answer 17

Blood type

Question 18

Name some characteristics of an ideal population

Answer 18

• Mutation can be ignored and migration is negligible
• Mating is random and there are no selective pressure
• Allele frequency equal in sexes in large population

Question 19

Do mutations increase or decrease proportion of new alleles?

Answer 19

Increase

Question 20

What else increases the proportion of new alleles?

Answer 20

Migration and intermarriage

Question 21

Give an example of migration and proportion of alleles

Answer 21

60% of men in NW Scotland have Scandinavian DNA and leads to a hybrid population

Question 22

What does non random mating do?

Answer 22

• Increase mutant alleles

- Increase affected homozygotes

Question 23

Assorative

Answer 23

Shared characteristic

Question 24

Consanguinity

Answer 24

Close blood relatives

Question 25

Natural selection

Answer 25

Gradual process where traits become more or less common in a population

Question 26

Negative natural selection

Answer 26

Reduces reproductive fitness
Decrease prevalence of traits
Gradual reduction of mutant allele

Question 27

Positive natural selection

Answer 27

Increases reproductive fitness
Increase prevalence of adaptive traits
Heterozygote advantage

Question 28

Give some examples of heterozygote advantage

Answer 28

Cholera/ typhoid with CF
Sickle cell anaemia for malaria
G6PD for malaria

Question 29

What do large populations do to fluctuations?

Answer 29

Balance them out

Question 30

Genetic drift

Answer 30

Random fluctuation of one allele to high proportion of offspring - mutations widespread and neutral after a fire or ploughing etc

Question 31

Founder effect

Answer 31

Genetic drift causes this reduction in genetic variation when a small subset of large population establish new colony with limited variation eg Amish founded from a small number of German immigrants

Question 32

Bottleneck effect

Answer 32

Reduce genetic diversity

Question 33

Assortative mating

Answer 33

Polydactyl common in Amish due to intermating