Estimating Risk of Inherited Genetic Disease Flashcards

1
Q

Fitness

A

the relative ability of organisms to survive and pass on genes

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2
Q

How can alleles affect fitness?

A

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

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3
Q

Population genetics

A

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

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4
Q

Why do relative frequencies remain constant?

A

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

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5
Q

What assumptions underlie HWE?

A
  • 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
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6
Q

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

A

introduction of new alleles as a result of migration or intermarriage

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7
Q

What increases the proportion of new alleles?

A

mutations

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8
Q

What does non-random mating lead to?

A

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

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9
Q

Assortative mating

A

choosing of partners due to shared characteristics

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10
Q

Consanguinity

A

marriage between close blood relatives

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11
Q

Natural selection

A

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

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12
Q

Describe negative selection

A
  • reduces reproductive fitness
  • decreases the prevalence of traits
  • leads to gradual reduction of mutant allele
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13
Q

Describe positive selection

A
  • increases reproductive fitness
  • increases the prevalence of adaptive traits
  • hererozygote advantage
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14
Q

What can be seen in small populations?

A

genetic drift which causes a founder effect

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15
Q

Genetic drift

A

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

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16
Q

founder effect

A

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

17
Q

Describe genetic drift.

A
  • 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
Q

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

A

Ellis-van Crevald syndrome

19
Q

Applications of HWE?

A
  • useful for calculating risk in genetic counselling

- useful for planning population based carrier screening programmes