PSY2003 S2 W2 Behavioural Genetics 2

Question 1

How to calculate heuritability?

Answer 1

Vp=A2+C2+E2

V is the variance of a trait
A is the genetic component
C is the common or “shared” environment (anything in the environment that makes the traits similar across twin pairs)
E is the “non-shared” environment (anything in the environment that makes the traits dissimilar across twin pairs)

Question 2

What is the 1920s concept of criminal Brain?

Answer 2

Neuroscience concerned with what might make someone criminal. Mental diseases – 50 criminal brains – you can tell if they were a criminal and what type of criminal by looking at their brain (shape) (e.g. narrow/broad).

Daily Mail – talked about how particular variance or form of this genes you were more likely to part take in criminal/anti-social behaviour. Criminal DNA

Question 3

What is meant by Genotype?

Answer 3

genetic information that an organism has, specifically based on alleles.

Question 4

What is meant by Phenotype?

Answer 4

physical expression of a gene

Question 5

What is an allele?

Answer 5

specific varaited

Question 6

What is heterozygous?

Answer 6

Having two different allele of the same gene

Question 7

What is Homozygous?

Answer 7

Have two forms of the same allele for the same gene

Question 8

How are genes transcribed into proteins?

Answer 8

ARN; Amino Acid

Question 9

What is a phenotype?

Answer 9

Trait (e.g. yellow vs green)

Question 10

What is Genotype?

Answer 10

genetic material (e.g. GG)

Question 11

What is an allele?

Answer 11

different forms of a gene that control the same trait (G versus y)

Question 12

What would be a heterozygous pair and a homozygous pair? Which is dominant/recessive?

Answer 12

Heterozygous: Gy
Homozygous GG or yy

G is dominant to y
y is recessive to G

Question 13

What has this got to do with Psychology?

Answer 13

Gene for the serotonin transporter.

Question 14

What did Mendel discover ?

Answer 14

Stuffed pee plants – the pods can be green or yellow. Crossed green pods with yellow pods, offspring were green. Crossed the offspring and 1/4 was yellow.

G or y from each parent: GG Gy yy. Only if you had both y you could be yellow.

Question 15

What are the alleles for the serotonin transporter?

Answer 15

The gene for the serotonin transporter has 2 forms long (l) and short (s). Different levels of activity in hoovering up the serotonin. Not a pattern of dominant/recessive. The effects are additive

Question 16

What is an additive?

Answer 16

when there’s no dominant or recessive allele

Question 17

What are Deoxyribose Nucleic Acid?

Answer 17

Chromosomes are made of DNA. DNA has a particular structure, with based pair [AT GC]

Question 18

Why is Meiosis interesting when looking at behaviour genetics?

Answer 18

Slight interest because the pattern of inheritance. Genetic varies can occur during Meiosis.

Question 19

What does DNA make?

Answer 19

Proteins
DNA unwinds to replicate itself. Instead of getting a complimentary strand of DNA you get a complimentary strand of RNA (which only has one) mRNA: [CG AU] mRNA travels to ribosomes. Ribosomes goes along in triplets. It’s triplet has some mRNA that is associated with. mRNA brings amino acids to ribosomes, patterns of three

Question 20

What are proteins?

Answer 20

enzymes

Question 21

What are some important proteins in the brain?

Answer 21

Transporter proteins (dopamine/Serotonin), receptors

Question 22

What makes serotonin?

Answer 22

This is the enzyme that makes serotonin – that’s all you need to know! Determines how much serotonin you have! Tryptophan Hydroxylase (comes from your diet (turkey and eggs)) makes serotonin.

Question 23

What is the effect of the mutant form of tryptophan Hydroxylase gene?

Answer 23

Mutation, allele, different form of Tryptophan Hydroxylase gene. You can’t make as much serotonin. In Vitro (grown in a dish) cells with this gene make 80% less serotonin than cells with more common gene.

Question 24

What about depressed patients and serotonin?

Answer 24

Serotonin is associated with mood which might make you more susceptible to mood disorders if you have the mutant form.

9/87 Depressed PTT with mutant form
3/219 Control with mutant form (Anxiety, alcoholism, family history of mental health problems.)
Rare mutant 12/306 but 3 times more in depressed patients than control.
If you have the mutant form of tryptophan Hydroxylase you have less serotonin and associated with depression and co-morbid conditions. This is accounting for a low number in both groups.

Question 25

What seems to result in mental health problems?

Answer 25

Gene for Tryptophan Hydroxylase: Mutant form seems to result in mental health problems. But…many people who are clinically depressed don’t have mutant form. Maybe other causes; environmental, genetics.

Question 26

What is DAT1 Gene involve?

Answer 26

DAT1 Gene – dopamine reuptake transporter – involved in cocaine addiction, ADHD and schizophrenia.

Question 27

What is associated with GABRA2?

Answer 27

GABRA2 – a GABA receptor (inhibitory) – associated with increased alcohol use, associated with conduct disorder and associated with epilepsy.

Question 28

How is comordibity important in behavioural genetics?

Answer 28

ASC and ADHD have a high comorbidity. Substance misuse and schizophrenia. ADHD and some substance misuse disorders

Question 29

What is Nicotine Acetylcholine receptor α4 Subunit Gene ?

Answer 29

Addiction in general ADHD

Question 30

How does serotonin transporter (protein) act?

Answer 30

Serotonin transporter (protein) acts more as a risk factor gene x environment interaction. Different activities of ST you could alter the serotonin in the synaptic cleft. 2 forms: alleles: long and short form.

Question 31

WHy is the allele called long or short?

Answer 31

gene is long and short, so it occupies a different length of the DNA. Short form more related to depressive symptoms than the long form

Question 32

What is the short form sometimes linked to?

Answer 32

The short form is sometimes linked to depression and sometimes isn’t! Could be psychological measures of depression are inaccurate or could be that the link doesn’t exist. Solution: Brain scanner

Question 33

What did Brain scanner find about short forms and depression?

Answer 33

Serotonin transport – took people with long or short form and looked at the brain. Measured if they had long or short form of ST. NO one was depressed even with short form ST. He got people to judge faces and looked at the activity of the amygdala. How active the amygdala is in the fMRI. Y axis – we see fearful face and short group shows a large response compared to long group. Higher brain activation to negative emotions for group with short form gene.

Question 34

What is 5-HT?

Answer 34

5-HT: chemical name for serotonin and the extra T is the transporter. 5HTT: serotonin transporter type.

Question 35

WHat does the short form of serotonin transporter gene do?

Answer 35

Makes the brain “over-respond” to negative emotions – short form – could lead to depression but no one had depression even in the short form group. Risk factor for depression but many people have (s) gene(s) and not depression Environment

Question 36

How does stress affect depression? | Environment Brown 1993

Answer 36

Depressed Patients: Severe stress in previous year [84%] Control: Severe stress in previous year [32%] More likely (84%) to have experience severe stress in previous year before a depression diagnosis, compared to control (32%)

Question 37

What is the diathesis-stress model?

Answer 37

Risk factor Genes: Stress: no stress Depressed patient: not depressed No risk Factor Genes: Stress: Not depressed No stress: not depressed

Question 38

What did Caspi et al. 2023 find?

Answer 38

Measured stressful events (loss of a parent) divided subjects into groups based on forms of serotonin transporter gene Measured depressive syntoms. Results: No difference in number of stressful events between genetic groups Depressive symtoms: nb of stress full life event: non significant Genotype: non-significant Interaction: highly significant Graphs: ANOVAs depression symptoms (y), (x) number of stress life events. s/s, s/l, l/l. s/s has significant increase in depressive symptoms. Interaction of gene x environment interaction.

Question 39

What is the summary of the Caspi Study?

Answer 39

5HT-T gene short (s) and long (l), more short forms you have more likely to be depressed (ss versus ls versus ll) BUT only when combined with stressful life events. (G X E interaction) Caspi Study showed very nicely the gene X environment interaction and diathesis stress model. Caspi Study is evidence. Gene and environment are involved.

Question 40

What did Caspi et al. 2003 find? | reading

Answer 40

5-HTT gene interacts with life events to predict depression symptoms, an increase in symptoms, depression diagnoses, new-onset diagnoses, suicidality, and an informant’s report of depressed behavior. The interaction showed that the effect of life events on informant reports of depression was stronger among individuals carrying an s allele than among l/l homozygotes 5-HTT gene interacts with life events to predict depression symptoms, an increase in symptoms, depression diagnoses, new-onset diagnoses, suicidality, and an informant’s report of depressed behavior