Genetic Basis of Multifactorial disease Flashcards

1
Q

Describe the contribution of genetic and environmental factors

A

Some diseases are almost exclusively genetic (eg, cystic fibrosis) some diseases are a combination of both genetic and environmental (eg, heart disease) and some are almost exclusively environmental (eg, trauma) but still has some genetic factors

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2
Q

What is quantitative inheritance?

A

Complex disorders and continuous traits which are influenced by multiple genes and multiple environmental factors

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3
Q

What are single gene disorders?

A

Deterministic

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4
Q

What are complex traits?

A

Even if you have all susceptibility alleles, disease still depends on environmental hazards.

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5
Q

What is the liability threshold model?

A

Where all the factors which influence the development of a multifactorial trait/disorder can be considered as a single entity

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6
Q

What is to the right of the threshold on a liability curve?

A

The incidence of disease in the general population

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7
Q

What is the familial incidence?

A

The proportion above the threshold on a liability curve

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8
Q

What is heritability of a trait/disease?

A

It is the proportion of the total variance that is genetic

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9
Q

What is the overall variance of a phenotype?

A

The sum of the environmental and genetic variance.

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10
Q

What is polymorphism?

A

Any variation in the human genome that does not cause a disease on its own but can predispose to a common disease.

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11
Q

What is synonymous polymorphism?

A

Changes in DNA sequence that doesn’t change the amino acid or subsequent protein

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12
Q

What is non-synonymous missense polymorphism?

A

Changes in the DNA sequence and amino acid and protein produced

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13
Q

What is non-synonymous nonsense polymorphism?

A

Changes to DNA sequence to code for a premature stop codon.

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14
Q

What are some of the limitations of family studies?

A

It does not take into account the risk caused by shared environment such as a familial predilection for hamburgues in siblings

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15
Q

How will the liability curve appear for affected relatives?

A

It will shift to the right as the familial incidence is higher than the general population

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16
Q

Describe why 1st degree relatives of an affected person who in the lower risk group are more likely to get the disease?

A

For the person in the lower risk group to be affected they would have to have had a greater number of risk factors therefore their relatives are more likely to also have a greater number of risk factors.

17
Q

What are some of the limitations of twin studies?

A

It doesn’t take into account that being a monozygotic twin can be a predisposing factor for a disease

18
Q

What are the ways of working out if a disease phenotype has genetic contribution?

A

By recurrence risk in siblings and twin studies

19
Q

What are some of the limitations of association studies?

A

Difficult if you don’t know what gene or polymorphism to look at and association could be due to chance or to population stratification.

20
Q

How can you find out if a polymorphism contributes to a disease?

A

Via association study methods - looks at the affected individuals and what polymorphism is increased. Or test the whole genome - Analyse the polymorphisms in a disease and control population.

21
Q

When can you suspect a single gene disorder

A

If you see a really severe version of a disease that is usually multifactorial

22
Q

For multifactorial conditions there is a higher recurrence risk if?

A

There are more affected family members and more severely affected family members.

23
Q

What informations does heritability provide

A
24
Q

Liability / susceptibility for a certain disorder: example

A
25
Q

What should we do for multifactorial conditions

A