Estimating Risk of Inherited Genetic Disease Flashcards

1
Q

Define Fitness

A

The relative ability of organisms to survive (long enough) to pass on their genes.

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2
Q

If an allele reduces reproductive fitness, what is this known as ?

A

Deleterious allele

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3
Q

If an allele increases reproductive fitness, what is this known as ?

A

Advantageous allele.

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4
Q

If an allele doesn’t impact reproductive fitness, what is this known as ?

A

Neutral allele

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5
Q

Name two diseases that are recessive.

A

Sickle cell disease
Thalassaemia

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6
Q

Where are de novo mutations common?

A

In dominant disorders especially where disease reduces reproductive fitness

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7
Q

What kind of mutation is responsible for learning difficulty syndromes?

A

De novo

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8
Q

People : 800 AA + 190 Aa + 10 aa = 1000 total

Work out the genotype frequency for the following-
AA
Aa
aa

A

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

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9
Q

People : 800 AA + 190 Aa + 10 aa = 1000 total
Alleles : 1600 A + (190 A + 190 a) + 20 a = 2000

Work out the allele frequency for the following-
A(p)

A

1600 + 190 = 0.9
————–
2000

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10
Q

People : 800 AA + 190 Aa + 10 aa = 1000 total
Alleles : 1600 A + (190 A + 190 a) + 20 a = 2000

Work out the allele frequency for the following-
A(q)

A

2000

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11
Q

p=q=>?

A

1

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12
Q

State the equation for the Hardy Weinburg.

A

p^2 + 2pq + q^2 = 1

^=squared

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13
Q

P^2=?

A

p^2 = dominant homozygous frequency (AA)

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14
Q

2pq = ?

A

2pq = heterozygous frequency (Aa)

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15
Q

q^2 =?

A

q^2 = recessive homozygous frequency (aa)

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16
Q

Discuss the frequency of allele frequencies

A

Allele frequencies remain constant generation to generation.

17
Q

Discuss the relative proportion of genotype frequencies

A

Relative proportion of genotype frequencies remain constant generation to generation.

18
Q

What are some of the assumptions made when using the HW equation?

A
  • Mutation 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
19
Q

What increases the proportion of new alleles?

20
Q

What does the introduction of new alleles through migration/intermarriage lead to?

A

New gene frequency in hybrid population.

21
Q

What does non-random mating lead to?

A

An increase mutant alleles, thereby increasing proportion of affected homozygotes

22
Q

Define Assortative mating

A

Choosing of partners due to shared characteristics
Deafness & sign language

23
Q

Define Consanguinity

A
  • Marriage between close blood relatives.
24
Q

Name two founder effects

->(the reduction in genomic variability that occurs when a small group of individuals becomes separated from a larger population)

A

Physical or cultural isolation

25
Describe natural selection.
A gradual process by which biological traits become either more or less common in a population.
26
Discuss Negative selection
- Reduces reproductive fitness. - decreases the prevalence of traits. - leads to gradual reduction of mutant allele.
27
Discuss positive selection
- Increases reproductive fitness. - Increases the prevalence of adaptive traits. - Heterozygote advantage.
28
What three recessive conditions mean that you are resistant to malaria?
Thalassaemia Sickle cell anaemia Glucose-6-phosphate dehydrogenase deficiency (G6PD)
29
If you have cystic fibrosis, what will you be resistant to?
Cholera/Typhoid
30
If you have Congenital Adrenal Hyperplasia (CAH) what will you be resistant to?
Influenza B
31
If you have GM2 gangliosidosis (aka Tay-Sachs) what will you be resistant to?
TB
32
What can smaller populations have?
Genetic Drift Founder effect
33
Define genetic drift.
Random fluctuation of one allele transmitted to high proportion of offspring by chance.
34
Define founder effect
The reduction in genetic variation that results when a small subset of a large population is used to establish a new colony.
35
Discuss genetic drift.
Mutations (alleles) 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
36
What does the bottleneck effect do?
Reduces genetic diversity
37
What is the HW equation useful for?
Useful for calculating risk in genetic counselling Useful for planning population based carrier screening programmes