Quiz #6 Virology 409
30 September 1999 (a double quiz)
.....It was a long drive especially having to sit so long with sore muscles from climbing even the top portions of the Grand Canyon. They watched their ecology notes come to life as they had only been in the barren scrub of the Mojavé Desert a few days ago, and now they were climbing out of grassy valleys up into the dense ponderosa pine forests surrounding the San Francisco Mts, upon whose hip sat Flagstaff AR. They then descended back onto more desert where they visited Meteor Crater Natural Monument (bought a few pieces of meteor), then stopped for an early lunch at the Petrified Forest Nat'l Pk, and had a later lunch in Gallop NM (bought some Navajo and Hopi sand paintings). They all got out of the car a few miles further to have their picture taken at the Continental Divide sign (7,700 ft above sea level). A couple of hours later they crossed the Rio Grande and zipped through Albuquerque, a huge city set in the middle of nowhere, and had dinner in a little yuppy place on the Plaza in Santa Fé, where "the Trail" ended.
.....They were joined by Harjot, who was one of the Los Alamos Nat'l Lab grad students. She told them about a similar virus upon which she had been doing some radioimmunochemistry experiments. For dessert, the group was joined by Dr. Sagaroff, who was Wilbie's uncle's neighbor's friend. When asked where their project was going, Cheryl piped up that Harjot had just told them of a virus that seemed very closely related. This might negate the need to work with the endangered saguaro hosts.
....."Lez me tell you zometing you vill find wery interestink," began Dr. Sagaroff, who then went on to describe this virus in greater detail. It was a pathogen of the plant Opuntia mexicana, a type of cholla (say it in español: choy' ya) which was very common around the Rio Grande. "Perhaps you have zometing like her in Wirgeenia - perhaps Opuntia humifusa - and perhaps she has a wirus like your SMV. Lez me tell you zometingz about our mexicana wirus."
.....She went on to tell them about some data that her lab had just gotten that day. Earlier they had found that thin slices of the plant could be placed on minerals+agar in a lighted petri plate. Cells then began to grow or migrate out onto the agar forming greenish haloes around the bits of slices. They then found that their MMV would grow very rapidly in these 'halo cells.'
.....That was all this group of hyper-bright students needed. The next day, they took some of those cells and infected some with MMV and others they pretreated with two antibiotics before adding MMV. They got these results with these transcription and translation inhibitors (which showed no deleterious activity on the mexicana cell cultures when used without MMV). What is the significance of this?
.....Next they wanted to do a dual labelling study to look at the complementarity between the host and viral genomes. In the host DNA, they wanted to incorporate tritium in the form of thymidine, and in the viral RNA, they wanted to use 32P- orthophosphate, which emits beta particles of 100-times the energy as those of tritium. To do this, they took some of Dr. Sagaroff's mexicana-dsDNA that had been isolated from cells grown on plates containing tritiated thymidine. This DNA was boiled and fast-cooled. To this was added some variously pretreated MMV-RNA's that had been isolated from viruses grown in cells that were labelled with 32PO4-3. CsCl isopycnography gave the results shown in Fig 5-2. What is the significance?
.....Meanwhile, Mary Lou was looking through her brother's notebook and found a page of scribblings she thought were his plans for the next experiment. So she set out to beat him to it: it was the basic hyperchromic effect, which had actually been done back in Vegas while she was holding down the table at the Vegas Hard Rock café with its huge guitar-sign out front. Wisely setting out to make a practice run so as to acquaint herself with the technique, she grabbed whatever RNA's were at hand. Jimmy, her heart throb, gave her his remaining samples of native, RNase-1 treated, and RNase-2 treated RNA's. (The latter two were re-isolated earlier by Cheryl to remove any residual free bases left over from the RNase digestions.) These Mary Lou put in a large waterbath and began the long and tedious heating, and following the readings from the automatic spectrophotometer:
.....As it was getting late, she switched off the waterbath heater, and went to find her colleagues and went back to the dorm to which they had been assigned outside the lab at Los Alamos.
.....The next morning, Jason went to see if his sister had cleaned up after her work the previous day. Before you know it, he came running down the hall hollering excitedly and waving the analyzer's printout sheet. He was yelling something about a great finding. What was it?
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