We selected the horn gene because of its high prevelance, and the ease with which one can observe mutant events. Basically the horn gene expresses two subunits - the "bulb" and the "trumpet". At this point of our studies, its not clear whether expression of bulb and trumpet actually arises from a single expression of the horn gene or whether they are in fact, the result of co-expression of a bulb gene and a trumpet gene. In either case, expression of the horn gene results in a "horned" auto while failure to express results in the "hornless" auto. Within the class of horned autos, we have observed both gene products (bulb and trumpet) as well as bulbless and trumpless horns. Bulbs vary in size - while trumpets vary in configuration (see bottom of this page for examples).
In any study of noise, its necessary to first establish a baseline. We start with a summary of various modes of transport seen on the streets of Chennai. So here is a nice view of Mt Road with motorcycles and distant bus:
There is the usual spectrum of transport - ranging from the automobile to ladies (I never saw a man carrying something on his head). motorized 3 wheeler with driver:
There is the auto-rickshaw - a sort of three wheel contraption, equipped with noise-making horn and sometimes grumpy driver
There are bicycles
Then there are tricycles
and some unusual 2 wheet barrel transporter:
Here is a frequently seen transport - the oxcart - usually without ox. This one travels up and down TTK road, moving dirt between two locations. This morning - the driver stopped for a position in our photo-essay.
Finally, there is the real king of the law of large noises - the bus
and water trucks and lorries
There are two primary components - the bulb, and the trumpet. Here, we can see insertion and deletion at work. note a bulbless:
and trumpetless horn:
Here are examples of mutant horns (bulbless [deletion] and broken):
With bulb, but broken
Here is an example of overexpression of the bulb gene and underexpression of the trumpet gene
Finally, here is an example of correct expression, but a post-translational alteration resulted in a spiral trumpet:
[Nore on Dec 18] Yesterday, I had the good fortune to catch an auto equipped with an overexpressed trumpet.
As seen form the inside - here is what the overexpressed bulb looked like
And you can get a very good impression of use - after viewing this photo taken along the longitudinal axis of the trumpet and then observing the driver's perpendicular arm angle when squeezing the bulb.
[Dec 19 2002] Today we discovered an interesting variant of the expressed products of the horn gene: the double-trumpet gene:
The result is quite interesting and when stopped, the double trumpet equipped auto is the source of admiration from local children:
C. Frank Starmer