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Flashcards in Estimating risk of inherited genetic disease Deck (33):
1

Fitness

Relative ability of organisms to survive and pass on genes

2

What does fitness depend on?

Types of alleles eg neutral, deleterious or advantageous

3

Do deleterious mutations sometimes or rarely decrease fitness?

Sometimes

4

Do advantageous mutations sometimes or rarely increase fitness

Rarely

5

Frequency of alleles affect healthy population

Population genetics

6

1 gene with 2 alleles what are p and q

p = dominant q = recessive

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Genotype frequency

GG/total

8

Allele frequency

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

9

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

NO

10

Hardy-Weinberg principle

Use quadratics

11

What are constant generation to generation?

Allele frequency and relative proportion of genotype frequency

12

p squared = q squared = 2pq=

1

13

What can HWE allow?

Calculate risk in genetic counselling
Plan population based carrier screening programmes

14

p squared

Homozygous dominant

15

q squared

Homozygous recessive

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pq

Heterozygous

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When is HWE not always achieved?

Blood type

18

Name some characteristics of an ideal population

- 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

19

Do mutations increase or decrease proportion of new alleles?

Increase

20

What else increases the proportion of new alleles?

Migration and intermarriage

21

Give an example of migration and proportion of alleles

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

22

What does non random mating do?

- Increase mutant alleles
- Increase affected homozygotes

23

Assorative

Shared characteristic

24

Consanguinity

Close blood relatives

25

Natural selection

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

26

Negative natural selection

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

27

Positive natural selection

Increases reproductive fitness
Increase prevalence of adaptive traits
Heterozygote advantage

28

Give some examples of heterozygote advantage

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

29

What do large populations do to fluctuations?

Balance them out

30

Genetic drift

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

31

Founder effect

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

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Bottleneck effect

Reduce genetic diversity

33

Assortative mating

Polydactyl common in Amish due to intermating