A fly's life

Today in genetics practical we had to dissect Drosophila larvae in search for inverted chromosome sequences..

I'll put part of the Prac manual in here:
Purpose of this experiment: Isolating polytene chromosomes from the salivary glands (from 3rd instar larvae)... The method for this isolation is detailed below.

1. Selection of Larva
(in my own words) Use forceps to choose for a large, fat larvae, that is still moving, from the container holding the larvae. Pinch it out and place it on a slide, then clean off excess food particles that may be sticking around the larvae's body.. (it's constantly twitching and squirming, and after i release it into a puddle of saline it sort of felt the freedom and wriggle away...)
Place slide against a black background, observe the larvae under the dissecting microscope.
(I just put the larva on my slide for a while without observing it under my microscope, i did something else; when i came back its not in the view of the microscope anymore... it keeps wriggling away...)

2. Dissection of Larva
(from prac manual) Holding the tail end of the larva with the forceps or needle (i use needle), place the second pair of forceps or needle, just behind the mouthparts (these are the little black hooks at the front end of the animal that are usually moving in and out). Hold the larvae steady and in a slow movement pull away the head. Hopefully, the salivary glands (which are translucent) will pull free. Note it is critical that you do not let the glands dry out while they are sitting on the microscope stage.

*For this step i tried twice actually (which means i killed 2 larva instead of just one, because the first attempt failed-- so did the second attempt =P) It says i have to hold the larvae steady right... so i used my needle to pin the tail so it can't move forward; at this point the larvae must have felt the excruciating pain on its bottom so it was writhing pitifully trying to free itself (but to no avail of course) (i said sorry to the larvae)... in order to cease its suffer quicker, i tried to pinch and get hold of the head to pull it off....
Forcefully (but also gently) i pulled and pulled, hopefully the glands will be pulled out from the front end, starting from its hook to its 'throat' and then the gland and then everything else...
HOWEVER (rmb i poked the needle on its bottom?) instead of being pulled apart from the head, the bottom bit was torn. WAS TORN OMG... under this circumstance i pinned the needle towards its abdomen instead (move forwards, avoiding the torn part) and then try pulling again in hope of pulling the gland from the head... ... ... ... ... ended up tearing the abdomen @_@'
So, there i was with my larvae's intestines instead of the gland...

The exact same process occured on the other unlucky larvae... In the end i reckon there's no use killing the 3rd one, since i've 'dismantled' the whole digestive structure i might as well trace the gland from the opposite direction... That's why i ended up having twice the amount of salivary glands than other prac classmates are having...)

3. Preparation of the Salivary Glands
Remove as much of the other debris from the slide, making sure you know where the glands are positioned on the slide. Apply a tiny drop of 45% acetic acid onto the glands and wait 1 minute... the rest of the step is not essential so i didnt put it here..

4. Squashing and Staining the Salivary glands
Place a drop of orcein stain (to stain the DNA) onto the glands and allow to stain for 10 minutes- then apply a coverslip (the small square piece of glass that covers the specimen on the slide). Tap coverslip gently with the blunt end of a dissecting needle which helps in disrupting the tissue and 'speading' the chromosomes.

Fold a tissue and place it on the bench in front of you. Invert the slide onto this piece of tissue so that the coverslip is facing down. Fold the tissue over the top of the slide- effectively sandwiching the slide in the tissue. Then stand up and exert through the slide a firm and steady pressure with your thumbs placed over the area where the coverslip is located. (Have to be careful not to break the slide into two) Apply the pressure for at least 15 seconds.

5. Observing the Chromosomes
... look at the slide under compound microscope....

Haha sorry i must have bored you out reading the procedures... but in the end i can't find any chromosomes i'm supposed to find... i was pretty sure my techniques are correct and that i've got the right gland... but still.. its alright because only a few in the whole class successfully got that chromosome in their slide...

I have put the title of this blog as it is because i want to state how innocent a fruit fly can be, almost half of the experiments in my prac manual involves this species of fruit fly... but don't be afraid they won't extinct so easily because scientists are constantly using them as model organisms (to let them mate and look at the offspring)...
Last week i had to look at the fly's eyes, the colour and whether its smooth or has 'fur-like' structure, how the fur on its thorax is like... whether the 'fur' is long and straight, or somewhat bent like an 'L' shape...
After the prac i was almost seeing flies everywhere... (because i have to look into the microscope and count how many of those flies share the similar characteristics.... all in all i've looked at 67 Drosophila flies...rmb they're only 3mm max in length)...

I thought it's just another prac and another dissection so i didn't thought it as interesting as it would sound, until when i was chatting with Rhian and with mz (on the phone) and after describing the entire process, their laughter made me realize that it is rather interesting.. so i blogged it down now to share...

Well, Putty, i'm thinking of going to NZ this hol too.. but i hav to see if i'm lucky enough to be selected for a research program... and i'll see how the schedule is like...
Jia you putty! Rhian, must enjoy the rest of the holidays... remember not 'xia4 dan4', next time say 'fang4 bomb'... Mz, (who is behind me now) still listening to music and browsing through ppl's facebook profile?
=P till next time~