Lecture 14 - Genetics, Epigenetics, Brain and Behaviour Flashcards
1
Q
What does our unique behaviour profile arise from?
A
- Individual DNA sequence
- Env factors we are exposed to throughout life
- Complex interaction between both of the above
2
Q
How is DNA inherited?
A
- Via chromosomes
- Somatic cells contain 46 chromosomes but 23 in germ cells (sex)
- Split into autosomes and sex chromosomes
- XX = female, XY = male
3
Q
Where do polymorphisms occur?
A
- At a single base pair (1 in every 300) called SNP
- Larger chunks of DNA (deletion) called CNV
4
Q
What is a gene?
A
- A stretch of DNA that encodes a functional molecule
- Genes are transcribed into RNA molecules to be expressed
5
Q
What are the main parts of DNA?
A
- Exons are important and only make up 1-2% of DNA
- Junk DNA = regulatory DNA
6
Q
What happens to RNA?
A
- Retained in nucleus or can be transported
- mRNA are moved to ribosomes and translated to specific polypeptides to build a protein.
7
Q
What are the 4 types of proteins?
A
- Structural
- Catalytic
- Regulatory
- Receptors
- Transporter
8
Q
How do genes make different proteins?
A
- One gene can give slightly different transcripts (splice variants) to make slightly different proteins
- Complexity explains sophisticated brain functions (because of different methods of splicing)
9
Q
Why must DNA be read differently in different places?
A
- All cells of body have the same DNA
- Cells from different organs can be different
- Cell functions change over time because genes are switched on/off
10
Q
What is an example of why genes must be read differently in different places?
A
- STS is present in all cells
- Only being read in a certain part of the brain
11
Q
How is gene expression regulated?
A
- Extent to which RNA polymerase can bind to the start of the gene and continue along the DNA sequence
- To be packaged in the nucleus, DNA is wrapped about histone proteins
- Form chromosomes
12
Q
How do you chemically modify chromosomes?
A
- Acetylation & methylation affect accessibility of the DNA and gene expression
- Chemical modifications to DNA e.g adding stuff to it. Influences binding of RNA polymerase.
- Methylation blocks RNA polymerase to the start of the gene = not read/expressed
13
Q
What is epigenetic modifications?
A
- Reversible & dynamic
- Modulated by cells env
- Env can affect epigenetic markers affecting expression and function
- Inc. drugs, toxins/trauma, signalling molecules, stress, diet
14
Q
Describe the study on mice:
A
- Pregnant mice and gave some genistein which promotes methylation and others were given control
- Pups exposed to genistein looked different to control e.g darker and non-obese
15
Q
Study about environmental stresses:
A
- During the Dutch Hongerwinter and Chinese Famine
- Pregnant women gave birth to smaller babies with increased risk of obesity and schizophrenia
- Evidence of children’s DNA with more methylation.
16
Q
Study of epigenetics effecting offspring:
A
- Mice learnt smell of cherry blossom = electric shock
- Bred to naïve females and dads were killed so cant interact with pups
- Tested pups by exposing them to the smell
- Pups with dads that were scared were also scared of the smell
- Dads mark in sperm via epigenetic signatures = altered methylation. When inherited it affected structure of olfactory circuits in the brain and therefore interaction.
17
Q
How is our raising affecting epigenetics?
A
- Rat mums either lick/groom/nurse or the opposite
- Once pups grown up, the ones with nice mums had lower stress responses
- Looked at methylation in gene for stress response, and found different levels.
- If you swap the pup mums, the epigenetics reverse and methylation increases/decreases after birth
18
Q
How does epigenetic variation phenotypic variability over time?
A
- MZ twins are more alike earlier in life
- Study examined epigenetic markers across the genome at two timepoints to see whether changes in time can explain increased phenotypic divergence
19
Q
What is evidence for an interaction between genes and the env?
A
- Longitudinal study
- Looking at serotonin and depression
- Gene making transporter comes in two versions (long/short alleles)
- There is a known relationship between stressful life and likelihood of depression
- Results show no stressful life events = genetics don’t matter, but stressful life events = more likely for depressive symptoms. L/L = less vulnerable, S/S = more vulnerable
20
Q
What are polymorphisms?
A
- Slight variations between individuals at particular genomic sites
- Affect DNA function = individual differences
