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Flashcards in Estimating Risk of Inherited Genetic Disease Deck (39)
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1

Define fitness

The relative ability of organisms to survive and pass on genes

2

How can alleles affect fitness

In most cases not at all (natural allele)
Sometimes decrease (deleterious allele)
Rarely increase (advantageous allele)

3

What is population genetics

The frequency of alleles in the whole population affects the health of the population

4

How many alleles does a gene have

2

5

If 800 people have the genotype AA, 190 Aa and 10 aa out of the population of 1000. Calculate the genotype frequency of each

AA - 800/1000 = 0.8
Aa - 190/1000 = 0.19
aa - 10/1000 = 0.01

6

Calculate the allele frequency of 800 people with the genotype AA, 190 Aa and 10 aa out of the population of 1000

Alleles: 1600 A + (190 A + 190 a) + 20 a = 2000
Frequency of A (p) = (1600 + 190)/2000 = 0.9
frequency of a (q) = (190 + 20)/2000 = 0.1
p+q = 1.0

7

Overall how can genotype frequencies be calculated

AA:Aa:aa = p^2:2pq:q^2

8

Overall how can allele frequencies be calculated

A:a
= 2p^2+2pq:2pq+2q^2
= p(p+q) : q(p+q)
= p:q

9

What happens to allele frequencies from generation to generation

Remain constant

10

What happens to the relative proportion of genotype frequencies from generation to generation

Remain constant

11

How was the consistency of allele and genotype frequencies determined

Hardy-Weinberg equilibrium (HWE)

12

What would be required for the Hardy-Weinberg equilibrium (HWE) to occur

There must be an ideal population where:
Mutation can be ignored
Migration is negligible (no gene flow)
Mating is random
There is no selective pressure
Population size is large
Allele frequencies are equal in the sexes

13

What increases the proportion of new alleles

Mutations

14

How can new alleles be introduced

As a result of migration
Intermarriage which leads to a new gene frequency in a hybrid population

15

What does non-random mating lead to

An increase in mutant alleles therefore increasing the proportion of affected homozygotes

16

What is assortative mating

Choosing partners due to shared characteristics

17

What is consangunity

Marriage between close blood relatives

18

What is natural selection

A gradual process where biological traits become either increase or decrease in a population

19

What will negative selection do

Reduce reproductive fitness
Decrease the prevalence of traits
Leads to the gradual reduction of mutant alleles

20

What will positive selection do

Increase reproductive fitness
Increase the prevalence of adaptive traits
Provide heterozygote advantage

21

Who does sickle cell anaemia mainly affect and what does it provide resistance to

Tropical Africa
Malaria

22

Who does thalassaemia mainly affect and what does it provide resistance to

SE Asia/Mediterranean
Malaria

23

Who does glucose-6-phosphate dehydrogenase deficiency (G6PD) mainly affect and what does it provide resistance to

Mediterranean
Malaria

24

Who does cystic fibrosis mainly affect and what does it provide resistance to

Western Europe
Cholera/Typhoid

25

Who does congenital adrenal hyperplasisa (CAH) mainly affect and what does it provide resistance to

Yupik Eskimos
Influenza B

26

Who does GM2 gangliosidosis (Tay-sachs) mainly affect and what does it provide resistance to

E. European Jews
TB

27

What is the benefit of a large population

It can balance out fluctuations

28

What can a small population size exhibit

Genetic drift
Founder effect

29

What is genetic drift

A random fluctuation of one allele transmitted to a high proportion of offspring by chance

30

What is the founder effect

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