Klausur 2019

Question 1

Name and describe four advantages and two disadvantages of Drosophila melanogaster as a model organism. How many chromosomes does Drosophila melanogaster have? Which pair of chromosmes is called gomosomes?

Answer 1

Advantages:
- small genome
- known genome
- saves splace
- relatively easy to manipulate
- short life cycle
- low maintance costs
Disadvantages:
- research results not (100%) tranferable to humans because it is not a mammalian system
- high risk of contamination through other genotypes
- material can’t be easily frozen like bacteria
- handling requires more training due to small size

Drosophila has 3 pairs of autosomes and a pair of sex chromosomes (gonosomes), also known as the first chromosome.

Question 2

Briefly describe the structure and function of a chemical synapse (with a sketch). Describe the function and localization of the Drosophila-specific synaptic protein Bruchpilot (BRP).

Answer 2

BRP: cytoskeletal protein; important for integritiy of T-bars at pre-synaptic active zone; contributes to Ca2+ channel clustering

Question 3

What is an ERG and what is measured using this technique? Name one advantag and one disadvantage of this method. In the scheme below showing an ERG response of a wild-type fly, name the different components and explain their meaning and relevance for the analysis of an ERG phenotype.

Answer 3

Wild-type flies show a stereotypical response in ERG to a pulsed light stimulus: An on-transient from the laminar neurons (upward voltage spike), followed by a depolarization elicited from the photoreceptor cell and an off-transient (downward voltage spike) from the laminar neurons (repolarization), after which which the voltage trace rapidly returns to its baseline.
It has been shown that genetic differences/defects can lead to differences in this stereotypical response: For example, an ERG graph without an on-transient or off-transient indicates that the tested animals have an impaired signal transmission between the photoreceptor and the laminar neurons.

Question 4

Which neuropil is involved in learning and memory? Describe this neuropil anatomically. Name the different memory phase.

Answer 4

Neuropil: region/structure of high synaptic density with relatively low amount of cell bodies (soma) -> beetween glia
Mushroombody is involved in learning ans memory. It is innervated by olfactory projection neurons and the mushroom body neurons consist of Kenyon cells (clustered, ~2.500 in each hemosphere, are the soma of the mushroom body neurons), Calyx (draw-like; are the dendrites of the Kenyon cells; receive information from axons) and Mushroom body lobes (alpha and alpha’, beta and beta’, gamma (do not branch/bifurcate); alpha and beta are originated from same cell)
Memory phases:
- short term memory: for a few minutes; does not require repetitive training; in experiment flies were tested 5 Min after exposure to stimuli
- mid term memory: for up to few hours; in experiment flies are tested 1h after exposure to stimuli or 3h if interested in ARM and ASM
- long term memory: fpr 24h up to a few days; requires repetitive training (e.g. 10 times training session); in experiment flies were tested 24h after training

Question 5

How would you proceed to isolate and purify individual subfractiions such as synaptosomes, microsomes and mitochondria?

Answer 5

Electron microscopy?