Estimating Risk of Inherited Genetic Disease Flashcards Preview

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Flashcards in Estimating Risk of Inherited Genetic Disease Deck (19):
1

Fitness

the relative ability of organisms to survive and pass on genes

2

How can alleles affect fitness?

-Neutral allele: not at all in most cases
Deleterious allele: sometimes decrease
Advantageous allele: rarely increase

3

Population genetics

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

4

Why do relative frequencies remain constant?

Dominant conditions/alleles do not become more common at the expense of recessive ones

5

What assumptions underlie HWE?

-mutation can be ignores
-migration is negligible= no gene flow
-mating is random
-no selective pressure
-population size is large
-allele frequencies are equal in the sexes

6

What can lead to new gene frequency in a hybrid population?

introduction of new alleles as a result of migration or intermarriage

7

What increases the proportion of new alleles?

mutations

8

What does non-random mating lead to?

an increase in mutant alleles, thereby increasing proportion of affected homozygotes

9

Assortative mating

choosing of partners due to shared characteristics

10

Consanguinity

marriage between close blood relatives

11

Natural selection

a gradual process by which biological traits become either more or less common in a populaion

12

Describe negative selection

-reduces reproductive fitness
-decreases the prevalence of traits
-leads to gradual reduction of mutant allele

13

Describe positive selection

-increases reproductive fitness
-increases the prevalence of adaptive traits
-hererozygote advantage

14

What can be seen in small populations?

genetic drift which causes a founder effect

15

Genetic drift

ransom fluctuation of one allele transmitted to high proportion of offspring by chance

16

founder effect

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

17

Describe genetic drift.

-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

18

How can the founder effect be seen in the Amish of Pennsylvania?

Ellis-van Crevald syndrome

19

Applications of HWE?

-useful for calculating risk in genetic counselling
-useful for planning population based carrier screening programmes