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ME2019 PART 2 > Estimating Risk of Inherited Disease > Flashcards

Estimating Risk of Inherited Disease Flashcards

1
Q

What is fitness?

A

Relative ability of organism to survive (long enough) to pass on their genes

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2
Q

What can affect fitness?

A

Alleles

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3
Q

What are the 3 different kinds of alleles that can affect fitness?

A

Neutral allele (not at all in most cases)

Deleterious allele (sometimes decreases)

Advantageous allele (rarely decreases)

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4
Q

What is an allele?

A

A variant form of a gene

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5
Q

What is just an important as alleles for the fitness of human beings?

A

A child being brought up by family members and society

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6
Q

What is selective pressure?

A

Any phenomena which alters the behaiviour and fitness of living organisms within a given environment

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7
Q

What happens if selective pressure changes?

A

Importance of different alleles may change

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8
Q

What are the different kinds of genes that can become mutates?

A

Recessive genes

Dominant and X linked genes

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9
Q

What are some of the few noticable disease of recessive genes?

A

Sickle cell disease

Thalassaemia

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10
Q

When do recessive genes affect carriers?

A

When it is associated with selective pressure, such as malaria resistance

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11
Q

What is a de novo mutation?

A

A genetic alteration that is present for the first time in one family member as a result of a mutation

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12
Q

What are de novo mutations common in?

A

Dominant disorder, especially where the disease reduces reproductive fitness

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13
Q

How are genotype frequencies worked out?

A

People: 800AA + 190Aa + 10aa

AA = 800/1000 = 0.8

Aa = 190/1000 = 0.19

aa = 10/1000 = 0.01

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14
Q

How is the allele frequency worked out?

A

People: 800AA + 190Aa + 10aa

Alleles: 1600A + (190A + 190a) + 20a = 2000 in total

Frequency of A (p) = (1600 + 190) / 2000 = 0.9

Frequency of a (q) = (190 + 20) / 2000 = 0.1

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15
Q

What will p + q always equal?

A

1

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16
Q

What expression describes first generation genotype and allele frequencies?

A

Genotype: AA:Aa:aa = p2:2pq:q2

Allele: A:a = p:q

17
Q

What can you say about relavent frequencies through generations?

A

Remain constant

18
Q

What does the Hardy-Weinberg Equilbrium (HWE) state?

A

Allele frequencies remain constant generation to generation and so do relative proportions of genotype frequency

19
Q

What are the assumptions underlying the Hardy-Weinberg Equilbrium?

A

Mutations can be ignored

Migration is negligible (no gene flow)

Mating is random

No selective pressure

Population size is large

Allele frequencies are equal in the sexes

20
Q
A
21
Q

What do mutations increase the proportion of?

A

New alleles

22
Q

What does introduction of new alleles as a result of migration lead to?

A

New gene frequency

23
Q

What does non-random mating lead to?

A

Increase in mutant alleles, increasing the proporation of affected homozygotes

24
Q

What are the 2 kinds of non-random mating?

A

Assortive mating (choosing new partners due to shared characteristics)

Consanguinity mating (marriage between close blood relatives)

25
Q

What is assortive mating?

A

Choosing of partners due to shared characteristics

26
Q

What is consanguinity mating?

A

Marriage between close blood relatives

27
Q

What are homozygotes?

A

Individual having two identical alleles of a particular gene

28
Q

What are heterozygotes?

A

Individual having two different alleles of a particular gene

29
Q

What is the founder effect?

A

Loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population

30
Q

What are the different kinds of natural selection?

A

Positive selection

Negative selection

31
Q

What does negative selection do?

A

Reduces reproductive fitness

Decreases prevalence

Leads to gradual reduction of mutant alleles

32
Q

What does positive selection lead to?

A

Increase reproductive fitness

Increases prevalence of adaptive traits

Heterozygote advantage

33
Q

What can a small population size lead to?

A

Genetic drift

Founder effect

34
Q

What is natural selection?

A

Gradual process by which biological trates become either more or less common in a population

35
Q

What are some heterozygote advantages?

A

Sickle celll anaemia against malaria

Thalassaemia against malaria

Tay Sachs against TB

Cystic fibrosis against cholera

36
Q

What is genetic drift?

A

Random fluctuations in one allele transmitted to high proportion of offspring by chance

37
Q

What are some examples of the founders effect?

A

Cystic fibrosis in the faroes

Diminant BRCA1 and BRCA2 in Poland

38
Q

What are some applications of the Hardy-Weinberg Equilbrium (HWE)?

A

Useful for calculating genetic risk in genetic counselling

Useful for planning population based carrier screening programmes

ME2019 PART 2 (45 decks)

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