Topic 2.1 Epigenetics

Question 1

Epigenetics

Answer 1

is the study of how your behaviors and environment can cause changes that affect the way your genes work.

Question 2

Lissencephaly

Answer 2

A congenital condition associated with changes in the migration of cortical neurons, affecting brain development and mental functioning.

Question 3

Microencephaly

Answer 3

A condition associated with a smaller than usual head size at birth. It can be present in lissencephaly but also in other conditions.

Question 4

Miller–Dieker syndrome

Answer 4

One form of classic lissencephaly type 1

Question 5

What does the term spectrum refer to in the context of health conditions?

Answer 5

It refers to the occurrence of a set of symptoms that range in severity, as in autism spectrum disorders.

Question 6

ASD

Answer 6

autism spectrum disorders

Question 7

interneuron

Answer 7

A type of neuron that connects and modulates the activity of neurons within a limited region of the brain.

Question 8

GABA

Answer 8

neurotransmitter (gamma amino butyric acid).

Question 9

gene silencing

Answer 9

The process in which the expression of a gene is suppressed.

Question 10

gene activation

Answer 10

The process in which the expression of a gene is activated.

Question 11

epigenetic mechanisms

Answer 11

Mechanisms by which gene expression is altered by regulation of gene silencing and gene activation.

Question 12

FASD

Answer 12

Fetal Alcohol Spectrum Disorders.

Question 13

Why is asymmetric division important during development?

Answer 13

It is important because this is the process that is responsible for cell diversification.

Question 14

DNA methylation (CH3 tag)

Answer 14

off switch, less accessible histone

Question 15

Histone

Answer 15

compact spools of DNA

Question 16

Histone acetylation (COCH3)

Answer 16

on switch, more accessible DNA

Question 17

miRNA (non coding RNA, microRNA

Answer 17

blocks/destroys mRNA ability to make proteins

Question 18

glycolysis

Answer 18

This phrase literally means glucose splitting, a process that occurs during digestion.

Question 19

experimental study

Answer 19

A particular type of scientific study that is tightly controlled by researchers, the key feature being control over the independent variable.

Question 20

independent variable

Answer 20

A study variable that researchers manipulate in order to see an effect on the dependent variable.

Question 21

dependent variable

Answer 21

A study variable that is affected by manipulations of the independent variable and forms the measurable data in a scientific experiment.

Question 22

Where have you come across the PAFAH1B1 protein before?

Answer 22

Recall that there are reduced levels of this protein in Miller-Dieker syndrome due to the deletion of the LIS1 gene. PAFAH1B1 is involved in cell migration in cortical development.

Question 23

PAFAH1B1

Answer 23

a conductor for brain cell movement during development guides brain cells to their correct positions, ensuring the brain develops with the right structure.
Too little or mutated PAFAH1B1: The conductor is missing or doesn’t work properly, leading to brain cells getting lost or misplaced.

Question 24

If microRNAs that target the translation of mRNAs from the Dcx and PAFAH1B1 genes are reduced, would levels of Dcx and PAFAH1B1 increase or decrease and why?

Answer 24

They would increase. MicroRNAs interfere with translation so if levels of microRNAs are reduced, this interference would also be reduced, and the amount of protein produced would increase.

Question 25

Which of the following statements about epigenetic mechanisms are correct?

Answer 25

The correct answers are:

Methylation can affect the transcription of DNA.
Epigenetic changes are thought to link maternal diabetes and neural tube disorders.
MicroRNA can bind to mRNA and cause destabilisation.
Epigenetic mechanisms are thought to be involved in developmental conditions such as neural tube defects. Epigenetic mechanisms involve the addition of methyl groups to DNA or histones (methylation) or the addition of acetyl groups to histones (acetylation). Methyl and acetyl groups may also be removed. Epigenetic mechanisms can also involve alterations in the functioning of non-coding RNA, such as microRNA. Non-coding RNA refers to RNA that is not involved in the translation process whereby amino acids are pieced together to create proteins. MicroRNA is important epigenetically because it can bind to mRNA and cause destabilisation.

Question 26

Behaviourism originated in the work of Ivan Pavlov who studied a form of learning in dogs where two stimuli come to be associated. Later the renowned psychologist Burrhus F. Skinner built on Pavlov’s work to study how our actions come to be repeated. Before starting the association process Pavlov simply presented food to dogs to see what would happen. He noticed that they salivated in response to the food presentation. What is the technical name for this salivation in this context?

Answer 26

Unconditioned response
The salivation is a response from the dogs rather than a stimulus presented to the dogs. In the question context the dogs are salivating in response to food. The salivation is a natural reaction to food, so this would be an unconditioned response.

Question 27

Answer 27

The correct answers are:

Thalamus
Nucleus accumbens
Parietal lobe
Anterior cingulate cortex
Brainstem

Question 28

Select the appropriate brain structure from the drop-down box to match each description:

Answer 28

Sulci: Grooves on the surface of the brain.

Frontal lobe: Large region towards the anterior (rostral) region of the brain, involved in reasoning, movement and language.

Pons: Controls arousal levels, waking and sleep.

Pituitary gland: Found at the base of the brain and is responsible for the release of hormones into the blood.

Substantia nigra: Start of the dopamine pathway responsible for the control of movement.

Question 29

Which of the following statements about synaptic transmission are correct?

Answer 29

The correct answers are:

When an action potential reaches an axon terminal, it triggers the release of neurotransmitter.
There are enzymes in the synaptic cleft which break down neurotransmitters into their constituent molecules.
Activation of a receptor by a neurotransmitter can sometimes lead to an inhibitory postsynaptic potential.

Question 30

The excitatory neuron releases noradrenaline and the inhibitory neuron releases GABA. The firing rate of the neurons are represented by the graphs beside each one. What would happen to the firing rate in the postsynaptic neuron if a noradrenaline antagonist were added into the synapse? Choose the graph which best illustrates the change in firing rate.

Answer 30

The correct answer is B.

A noradrenaline antagonist binds to noradrenaline receptors, preventing noradrenaline from binding. The antagonist has no excitatory effect on the postsynaptic neuron. This means that the inhibitory effect of GABA released from the inhibitory neuron won’t be counterbalanced by the excitatory effect of noradrenaline and therefore the firing rate of the postsynaptic neuron will be reduced.

Question 31

Scientists are interested in a study to investigate changes in the size of the hippocampus in people with Alzheimer’s disease. Which of the following techniques would be best suited to this study?

Answer 31

MRI

DWI is a structural brain imaging technique which is used to map out pathways in the brain so it wouldn’t be suitable. Electrophysiology measures brain electrical activity rather than structure. fMRI also records brain activity rather than structure. MRI is a technique which can be used to visualise brain structures.

Question 32

Health condition A has a heritability value of 0.62 whilst health condition B has a heritability value of 0.97. Which of the following statements relating to the heritability of these conditions are correct?

Answer 32

The correct answers are:

Within a population 62% of the variance in condition A is determined by genes.
Genes play a greater role in the development of condition B compared with condition A
If a condition has a heritability value of 0.62 this is equivalent to 62% so 62% of the population variance in condition A is determined by genes whilst 97% of the population variance in condition B is determined by genes. Thus, genes play a greater role in condition B.