Topic 6 Part 1 Genetic issues in mental health Flashcards Preview

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Flashcards in Topic 6 Part 1 Genetic issues in mental health Deck (30)
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1
Q

Complex diseases

A
  1. Diseases resulting from complex interactions
    between genes (major genes, polygenes) and
    environmental exposures.
  2. Disease transmission in families does not fit a simple Mendelian pattern.
  3. Commonly exhibit variable expressivity,
    incomplete penetrance, or age-dependent effects.
2
Q

Variable expressivity

A
  1. The same trait/disorder is expressed differently in different people - mild and severe forms. Example: Neurofibromatosis.
  2. Different/many phenotypes associated with the same disease gene/mutation. Example: The same gene can cause OCD in one individual and motor tics in a different individual.
3
Q

Incomplete penetrance

A

When a person carries a gene, but there is no observable expression or phenotype.

4
Q

Age-dependent effects

A

Certain disorders have particular ages of onset; psychiatric disorders tend to have a later age of onset.

5
Q

Multifactorial

A

Phenotype determined by more than one gene, gene-gene interactions, and/or gene-environment interplay.

6
Q

Heterogeneity

A

Same phenotype caused by different genes or different interactions or variations in the same gene that is associated with differences in disease risk.

7
Q

Penetrance

A

How often a phenotype appears in an individual with a mutation.

8
Q

_ can be a marker of the severity of the index disorder.

A

Comorbidity.

9
Q

Assortative mating

A
  1. People tend to prefer similar individuals when choosing a partner, which also includes their health problems.
  2. Example: Among people with bipolar disorder, the likelihood their partner will have a history of mood disorder is 70%.
10
Q

Heritability

A
  1. The degree to which genetics contributes to the overall variability of a disorder within a population.
  2. A population statistic that expresses the proportion of the total phenotypic variation of a trait that is due to genetics.
11
Q

Heritability can be assessed through _

A

Familial aggregation studies, twin studies, and adoption studies.

12
Q

Copy number variants (CNVs)

A
  1. Variations in stretches of DNA found throughout the genome. These are often deletions or duplications.
  2. Most are benign, but rare large or de novo duplications or deletions have been associated with autism, epilepsy, learning disabilities, and schizophrenia.
  3. These can be tested for, although the testing is very expensive.
13
Q

The easiest way to measure heritability is through _

A

Twin studies - compare the concordance of monozygotic (identical) twins versus dizygotic (fraternal) twins.

14
Q

Epigenome/epigenetics

A
  1. Biochemical factors that alter gene expression but do not involve changes in the underlying DNA sequence.
  2. Examples: Alterations in methylation patterns or histone proteins.
  3. Epigenetic mechanisms have been suggested as possibly important in the onset of schizophrenia.
15
Q

For a given trait, a heritability of 0.5 means that _

A

50% of the variability in the population can be said to be related to genes.

16
Q

Increased susceptibility for developing Alzheimer’s disease is primarily associated with mutations on the _ gene on chromosome 19.

A

APOE.

17
Q

_ syndrome has been associated with schizophrenia.

A

Velocardiofacial.

18
Q

Candidate genes

A
  1. Identify genes involved in a biochemical process and then evaluate them for functional changes in affected individuals.
  2. Examples: Dopamine transmitters, serotonin receptors.
19
Q

Susceptibility genes are often looked for by _

A

Association studies.

20
Q

Genome Wide Association Studies (GWAS)

A
  1. Tests that look for areas of the genome associated with a certain disease by comparing the genomes of affected and unaffected populations.
  2. Can help to identify susceptibilty genes of small effect. Disadvantage: Hard to replicate.
21
Q

Pleiotropy

A

An effect in which a single-gene disorder results in problems expressed in many tissues and functions.

22
Q

Features of _ are consistent with early life reprogramming of genes in response to environmental effects.

A

DNA methylation.

23
Q

Psychiatric illness are often said to be _

A

Polygenic (many genes are involved, each of which as a small effect).

24
Q

The DSM focuses on defining psychiatric disorders in terms of _

A

Symptoms or phenotype (defining by etiology is considered too complex at this time).

25
Q

The association between bipolar disorder and schizophrenia is an example of a _

A

Cross-disorder overlap.

26
Q

Empiric risk

A
  1. A risk figure for a person being affected with a (usually) multifactorial disorder, obtained by observation and experience of many families where people have that disorder - based on statistics for a population.
  2. Usually expressed as a range.
  3. Identifying and explaining empiric risks is what much of genetic counseling is based on.
27
Q

Lithium, often administered to people with bipolar disorder, is associated with _ in fetuses.

A

Transposition of the great arteries.

28
Q

Endophenotypes

A
  1. Phenotypes associated with psychiatric illness but are more quantifiable, more common, and seen in more widespread conditions.
  2. Example: p50 EEG wave in schizophrenia, low response to alcohol.
29
Q

Behavioral phenotypes in genetic disorders

A
  1. Prader-Willi syndrome has an association with OCD, particularly compulsive eating.
  2. Neurofibromatosis has an association with ADHD.
  3. Down syndrome has an association with early-onset Alzheimer’s.
30
Q

Which statement or condition best reflects multifactorial inheritance?

A

The susceptibility to a problem is an inherited trait but development of the problem is related to environmental conditions.