Journal Club Throwbacks
In one of the last few lab meetings, we covered a paper showing that fruit flies fall for the same optical illusion humans do, perceiving motion in a stationary "rotating snakes" style image. Which two motion-detector neurons, when silenced, made the illusion disappear (and even reverse direction)?
T4 and T5
Name the independent visual units that make up the compound eyes of the fly.
Ommatidia
The foraging gene comes in two natural allelic variants named for how the larvae move while feeding. Name both.
rover and sitter
Name the first Drosophila mutant ever discovered
+bonus: Whose lab was it discovered in?
the white-eyed mutant
Thomas Hunt Morgan's lab (Columbia University, 1910)
A recent preprint looked at how flies track a vertical bar during flight. The key visual neuron (LC17) turned out to need a surprising kind of synapse for sustained tracking.
What kind of synapse?
+100 bonus: Name the kind of bar used in the tracking experiments that's only visible while it's moving and blends into the background the moment it stops.
Electrical synapses (gap junctions)
Bonus: A motion-defined bar
Flies don't turn smoothly; they change direction in rapid, ballistic steps, whether walking or in flight. What are these quick turns called?
Saccades (body saccades)
What special chromosomes carry markers and block recombination so a lethal mutation can be kept as a stable stock?
Balancer chromosomes
The very first Nobel Prize won using fruit flies went to Thomas Hunt Morgan in 1933. What discovery did he win it for?
The role of chromosomes in heredity
In a paper, two m⁶A "readers" had opposite effects on body weight in POMC neurons, one's knockout caused obesity, the other's knockout made mice resistant to obesity. Which pairing is correct?
A) YTHDC1 protects against obesity; YTHDF2 promotes it
B) YTHDF2 protects against obesity; YTHDC1 promotes it
C) Both protect against obesity
D) Both promote obesity
A — YTHDC1 protects (its knockout → obese), YTHDF2 promotes (its knockout → resistant). They're antagonistic, competing for the same POMC mRNA.
This is the wiring diagram of the fly's visual system. Name the four main neuropils the visual signal passes through, in order from the eye inward.
Lamina → Medulla → Lobula → Lobula plate
You've developed a new drug that you deliver through the flies' food, and you want to test whether it affects their activity levels over the next few days. Which two assays would you use to run this experiment properly?
The CAFE assay (Capillary Feeder) to confirm intake/dosing, and the DAM system (Drosophila Activity Monitor) to measure locomotor activity.
Who was the scientist who founded and worked on the Buridan's Paradigm?
Karl Georg Götz
Which microRNA did they identify as a regulator of the circadian locomotor activity-rest rhythm in Drosophila? And, conceptually, what does a microRNA do to a gene?
+100 bonus: What journal was this paper published in?
miR-275 (microRNA-275). A microRNA binds its target mRNA and silences it post-transcriptionally, blocking translation and/or triggering the mRNA's degradation (so less protein is made).
A: Genetics (Oxford Academic / Genetics Society of America)
What visual stimulus was presented
0 bars
You want to know whether your gene of interest is expressed at higher or lower levels in mutant vs. control flies. You extract RNA, but you can't run it on a qPCR machine directly; there's a conversion step first.
What is that intermediate step, and what enzyme carries it out?
+100 bonus: Once it's running, the machine reports a number for each sample that reflects how much of your target was present to begin with; an earlier signal means more starting material.
What's that value?
Reverse transcription, converting RNA into complementary DNA (cDNA), is carried out by reverse transcriptase.
The Ct (cycle threshold) value is the cycle at which fluorescence crosses the detection threshold; a lower Ct means more starting transcript.
The latest Nobel Prize involving Drosophila was awarded in 2017
What did they discover?
Name the scientists who discovered it(+100 for each name)
The molecular mechanisms controlling the circadian rhythm (the biological clock)
Jeffrey C. Hall
Michael Rosbash
Michael W. Young
What does DIO stand for, and how does it work within the Cre-lox system?
DIO:
These are the two classic models of how a single elementary motion detector computes direction: the fly's on the left, the rabbit's on the right. Both use two spatially offset inputs, a temporal delay (Δτ), and a nonlinearity.
Name both models, and state the key difference in their nonlinearity.
Left = Hassenstein-Reichardt detector (correlator), uses multiplication of the delayed and non-delayed inputs (enhances motion in the preferred direction).
Right = Barlow-Levick detector, uses subtraction/inhibition with the delay on the opposite arm (suppresses motion in the null direction).
The lab uses an Oroboros instrument. What does it actually measure?
It's a high-resolution respirometer that measures oxygen consumption (O₂ flux) of cells, tissue, or isolated mitochondria
In 1995, a Nobel Prize was awarded for mapping the genetic control of embryonic development. This work explained homeotic mutations, such as the famous Antennapedia mutant where what specific body parts mistakenly grow out of the fly's head instead of antennae?
Legs