MCB Lecture 26 Environmental and Genetic Interactions Flashcards Preview

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Flashcards in MCB Lecture 26 Environmental and Genetic Interactions Deck (20)
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Describe the nAChR's role in relay of environmental signals in drosophila

The environment is detected by nAChR. These caused changes in cells, and thus bring about a response in Drosophila.

Specifically, nAChR play a big role in the Jump Response, which allows Drosophila to escape from predators.
The jump response involves the eye detecting a shadow. This message is sent through neurons to muscles to cause them to contract. The chemical synapse requires nAChR to detect the Acetylcholine released at the synapse

1

Describe the jump response

A drosophila detects a shadow with there eyes
This message gets transduced and the Giant fibre is stimulated
The impulses travel down the giant fibre
nAChRs on Peripherally stimulating interneurons and Tergotrochanterol Muscle neurons detect the acetylcholine released by the giant fibre.
Tertrochanteral muscle and Dorsal lateral muscle are innervated and contract
The fly jumps and is removed from danger

2

Describe the circuitry responsible for the jump response

Eyes
Giant fibre
Peripherally synapsing interneurons -> dorsal lateral muscle motor neurons -> Dorsal lateral muscle
Tergotrochanteral muscle neurons -> Tergotrochanteral muscle

3

What is special about the nAChR across many different species?

Highly conserved DNA sequences, so the nAChR in different species are actually quite similar

4

Describe the structure of the nAChR

5 subunits (pentamer)
Each subunit has 4 transmembrane helices

5

Describe the function of the nAChR

Binds the ligand acetylcholine, which causes a conformational change
The conformational change is the channel opening
Sodium and calcium pass through the channel into the cell

6

Describe nAChR expression in muscle cells

Neuro-muscular junctions want even faster nAChRs.
In muscle cells, there is increased transcription of a gene coding for the epsilon subunit
This subunit out competes the gamma subunit in the nAChR
The receptor now has the epsilon subunit which causes the whole receptor to act more quickly

7

Describe how we know that it is nAChR that is vital for the jump response

When there is a mutation in Dalpha7, the flies do not show the jump response when put through the flight and olfactory test

When the nAChR transgender is put back into these flies, they show these responses

8

Describe how insecticides and exogenous compounds affect insects

These compounds directly target the receptors on post synaptic neurons
They jam the nervous system of the flies

9

Nicotine is ...?

A plant defence molecule

10

Neonicotinoids are ...

Man made insecticides

11

Spinosyns are ...

Bacterial attack/defence molecules

12

Venoms are ...?

Snake/spider defence molecules

13

Describe how some insects show resistance to insecticides

Mutations or deficits in some of the nAChR genes (Df2363) shows some resistance to insecticides

14

What is the mutation that leads to insecticide resistance?

Df2363

15

Insecticides target ...

Signalling circuitry

16

Mutagenesis increases ...

Variation

17

How are nAChRs involved in human disease?
Which diseases?

Epilepsy, Parkinson's, Schizophrenia, Alzheimer's

Channel dysfunction is involved in these diseases

18

What is epilepsy?
How can these symptoms be explained?

Epilepsy is sleep and awake seizures

There are mutations in the nAChRs (3 have been found)
This leads to increased excitability of the neurons and increased sensitivity to ACh

19

What is the pattern of inheritance of resistance to toxins?

It is recessive

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