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PSYC 441-MIDTERM > Lecture 5: Genetics > Flashcards

Lecture 5: Genetics Flashcards

1
Q

_________ is individual genetic make-up whilst ______ are physical and behavioural characteristics

A

Genotype – individual genetic make-up

Phenotype – physical and behavioural characteristics

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2
Q

Genetic epidemiology looks at whether there is evidence for _______________

A

heritability of a disorder

- If so, it looks at whether it appears to be a single gene or multiple genes?

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3
Q

What is the difference between Molecular genetics and molecular biology ?

A

Molecular genetics looks at whether the disorder is associated with specific genes and whether the disorder can be liked to gene variations.

Molecular biology, on the hand, looks at a candidate gene and what it does.

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4
Q

What have we learned from Family studies?

A
  • Risk is never as large as the genetic relatedness
  • First degree relatives have a greater risk than the population
  • MZ twins and children of two parents with SZ have the highest risk (about %50)
  • Siblings have lower risk than DZ twins
  • Parents have lower risk than children or siblings
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5
Q

Therefore, Risk not as great as _____________

A

genetic relatedness

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6
Q

What is meant by MZ twins not 100% concordant?

A

Genes are not enough, there’s environmental (pre- and post-natal factors)

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7
Q

DZ twins at higher risk than __________

A

siblings

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8
Q

What does DZ twins at higher risk than siblings mean?

A

Shared pre-natal environment is important

But not enough

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9
Q

Parents at lower risk than __________

A

children

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10
Q

Why would Parents be at lower risk than children?

A

Parents environment may have been different
ie, may not have had a parent with SZ
More stable family, higher SES, etc

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11
Q

How do we examine the relative contributions of genetic vs environmental factors?

A

Through adoption studies

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12
Q

What did the adoption studies of children with SZ mothers reveal?

A

Children of SZ mothers more likely to develop SZ

Twins reared apart have similar risk

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13
Q

But, children of SZ mothers adopted into __________ also show higher risk of developing SZ or SZ-spectrum disorders

A

low-functioning families

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14
Q

SZ is genetically _______, but not genetically ________

A

SZ is genetically mediated, but not genetically determined

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15
Q

A Meta-analysis showed that _____ of risk genetically determined; _____ environmentally determined

A

Meta-analysis: 81% of risk genetically determined; 11% environmentally determined

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16
Q

Relatives of people with SZ are also______ more likely to have schizotypal or paranoid personality disorder

A

4-5 times

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17
Q

Relatives of people with SZ also have a higher risk of ________

A

other SZ-spectrum disorders

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18
Q

Relatives of people with SZ do not have greater risk for _________

A

affective disorder, anxiety disorders or alcoholism

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19
Q

There may be a link between SZ and which other disorder?

A

Bipolar disorder

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20
Q

Which is Consistent with _______ conferring risk for psychotic disorders

A

multiple genes

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21
Q

In the study of transmission of genetic risk, transmission models predict ____________________

A

what we should see and then match it to the evidence

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22
Q

In the case of SZ, what type of model does not fit?

A

A model of simple transmission of a single gene (or locus) does not fit

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23
Q

In the multiple gene models of SZ, multiple genes contribute to a __________, _______, ________ to develop SZ

A

liability, susceptibility or predisposition

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24
Q

If there are multiple genes and inheritance is not simple, then genes are likely to be common _____________________

A

in the general population

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25
Q

The _______ model predicts that many genes contribute to risk, but no one gene or genes is necessary

A

polygenetic

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26
Q

The _____________ model proposes that risk is a continuum including genetic and environmental factors

A

multifactorial threshold

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27
Q

In the multifactorial threshold model, the presence of _____________________ adds to risk

A

each gene or environmental factor

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28
Q

Which model proposes that genetic risk factors interact?

A

The gene interaction model

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29
Q

The gene interaction model proposes that genetic risk factors interact. This is more consistent with _____________

A

fall-off rate of risk in relatives

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30
Q

Both ________ and ____________ likely contribute

A

Both additive risk and gene interactions likely contribute

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31
Q

Environmental factors are also critical. Give an example.

A

Prenatal stressors: maternal stress and starvation

32
Q

What did the Studies of the rate of SZ following famine in Netherlands show?

A
  • twice likely to develop SZ (environmental risk factor was famine)

***Children estimated to have been conceived during 1944-45 were twice as likely to develop SZ (But, only 25 cases!)

33
Q

What were the findings of the Anhui province study [ Rate of SZ following famine in China (1959-61)]?

A
  • Twice likely to develop SZ (environmental factor was famine)

Children born in 1960 and 1961 were twice as likely to develop SZ (large number of cases)

34
Q

What is the difference between linkage and association?

A

Linkage examines the whole genome looking for a relationship between a location and the disorder

Association tries to identify the relationship between one gene and the disorder

Moreover, Association Identifies a “candidate” gene based on relationship to one aspect of the phenotype
(e.g, A gene involved in dopamine regulation, brain region)

35
Q

What are the difficulties in conducting linkage?

A
  • Need multiple generations of the same family

- Hard to replicate

36
Q

Which one is the most powerful technique, linkage or association?

A

Association - More specific, powerful technique

37
Q

Linkage takes advantage of ___________________

A

naturally occurring gene recombination

38
Q

Genes that recombine frequently are ____________

A

further apart

39
Q

Genes that recombine frequently are further apart. Which means what?

A
  • Either on the same or different chromosomes

- Greater distance creates more chances for recombination

40
Q

Genes that recombine ________ are closer together or “linked”

A

less frequently

41
Q

With the recombination frequency of many genes, we can estimate ____________________________

A

how far apart they are and their relative locations

42
Q

Fewer generations make linkage studies _________

A

more difficult.

43
Q

What is another limitation of linkage studies?

A

You need large numbers of well-characterized families, which is not easy.

44
Q

The results of linkage studies to date are ________ and ________

A

not very conclusive and hard to replicate

45
Q

What happens once a location is identified? candidate genes known to be close to that location can be studied using _________________

A

association studies.

46
Q

There is evidence for linkage to ____________ and _________

A

several chromosomes and locations

47
Q

In regard to association, what does it mean to test whether affected people are more likely to have a certain gene or gene variant?

A

To find a candidate gene

48
Q

When associations look at individuals as opposed to families. Which specific question are they trying to answer?

A

Is a specific candidate gene more common in those with SZ compared to those without?

49
Q

Most candidate genes related to the ____________ systems

A

dopamine, serotonin and GABA

50
Q

Associations are limited by ____________

A

what we know about the pathophysiology of SZ

51
Q

What does GWAS stand for?

A

Genome-wide association studies

52
Q

GWAS Compare SZ and controls across the ________

A

entire genome

53
Q

In GWAS studies, how many gene locations can be assed at the same time? And what are they testing for?

A

Millions of gene locations can be assessed at the same time

Tests the inheritance of allele (gene) variants

54
Q

To control multiple comparisons, you need ______

A

very large samples

55
Q

What were the main findings of the Multi-center study (2009)? How many potential location did they find? On which chromosomes?

How many genes may contribute to the risk?

Similar genes also contribute to which disorders?

A
  • Found four potential locations (2 on chromosome 6)
  • Also found that thousands of genes may contribute to risk
  • Further, similar genes also contribute to risk for bipolar disorder and schizotypal personality disorder
56
Q

The Multi-sample GWAS Schizophrenia Working Group (2014) found _______ significant gene locations

A

108

57
Q

The Multi-sample GWAS Schizophrenia Working Group (2014) also found that these genes were expressed in which parts of the brain?

A
  • Frontal (working memory, planning, attention)
  • Angular gyrus (language)
  • Inferior temporal (complex visual, faces, memory)
58
Q

What was the key receptor in relation to SZ?

A

Dopamine D2 receptor

59
Q

What were the key immune response associated with SZ?

A

CD 19 and 20

60
Q

Name the three organs where these genes were less expressed (less relevant)

A

-Kidney, liver, muscles

61
Q

What can we conclude from GWAS studies

A

That there are many genes expressed in various locations but we don’t know if these are a cause or a consequence of SZ.

62
Q

However, what is one finding that is relevant from GWAS studies?

A

Greater risk with greater number of risk genes present

63
Q

Discussed the overview of results in GWAS studies.

  • The results of GWAS studies have _______________
  • Each gene contributes _________________
  • Supports the idea that _________________
A
  • not always reproduced the results of candidate gene studies
  • only a small effect
  • a large number of common genes with small effects contribute to the disorder
64
Q

What is meant by “a large number of common genes with small effects contribute to the disorder”?

  • Each common gene might account for_____ of the risk
  • Together, they would only account for ____ of the total risk
A
  • Each common gene might account for 1-2% of the risk

- Together, they would only account for 25-50% of the total risk

65
Q

What is the Common disease, rare variants hypothesis? (hint: what is the difference between common and rare genes in terms of effect?)

A
  • Many common gene variants of small effect
  • Rare gene variants of large effect
    (which can cause SZ)
66
Q

Further, 2009 study found that similar genes are associated with both SZ and _____ supports the idea of ______

A
  • Bipolar

- common gene spectrum

67
Q

What is a limitation of family studies?

A

Family studies assume that environment is constant and that genes and environment do not interact
(we know that this is not the case)

68
Q

What are other limitations of these types of studies we covered in this lecture?

  • SZ symptoms are _____________
  • No ________ at the individual level
  • Genetic studies are only as good as________
  • SZ and other disorders part of _____________
  • Overlap in risk with other disorders means ______
A
  • variable and sub-types (e.g., positive/negative symptoms) not clear
  • diagnostic bio-marker
  • as our diagnostic criteria
  • a spectrum with shared risk.
  • results are not specific
69
Q

We can conclude that SZ is genetically _______, but not genetically _______

A

SZ is genetically influenced, but not genetically determined

70
Q

___________ genes are involved.

The specific genes likely vary between ________ and _____________

A
  • Multiple
  • individuals
  • families
71
Q

Part of the genetic risk is accounted for by ______ variants that are _____ risk individually

A
  • common

- low

72
Q

There also an accounted for ________

A

rare, high-risk variants

73
Q

Risk is likely ______________________

A

Risk is likely additive (more risk genes = greater risk)

74
Q

SZ genes are also likely to interact with ___________

A

each other and/or with environmental risk factors

75
Q

Similar genes may be related to risk for other psychotic disorders, especially __________________

A

SZ spectrum and bipolar

PSYC 441-MIDTERM (12 decks)

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