Retroviruses, or more properly the lentiviruses, are fairly simple viruses
that have an RNA genome. Upon entering a cell, the enzyme, reverse
transcriptase, which is encoded by the viral RNA, makes DNA copies of the
RNA. The DNA then integrates into the cellular DNA where it can be passed
on to daughter cells. Then when the genomic viral DNA is copied into RNA,
it is able to be packaged into new virions to complete the life cycle.
The process by which viral RNA is reverse transribed into DNA is not
precise. Numererous examples are known in which the enzymatic machinery
"jumped" from the viral RNA to copy some cellular RNA, then jumped back to
finish copying the viral sequences. By this process, cellular gene
sequences can be incorporated into the viral genome and passed on to other
cells. There are many mouse, avian, feline and bovine retroviruses in which
genes that regulate cell growth have been incorporated into retroviral
genomes. These genes, when inappropriately expressed in infected cells,
cause malignancy, and are referred to as oncogenes. Michael Bishop and
Harald Varmus won a Nobel prize for recognizing that viral oncogenes arise
from cellular "proto-oncogenes."
The identity of this reverse transcription provides a wonderful example of
the Kuhnian-type of paradigm change. From the mid-50's to early 60's, it
became known that cellular DNA is copied into RNA and then into protein, and
this was referred to as the "central dogma." Howard Temin, while at Cal
Tech, learns that the activity of a cancer-causing retrovirus can be blocked
with reagents that act on RNA but not with reagent that work on DNA. Yet the
viral genome is passed along to daughter cells via cellular DNA. The only
way that this data made sense was to believe that RNA could be copied into
DNA--which was counter to the central dogma.
Howard received a lot of flak for proposing this model, but his conclusion
was certainly faithful to his data. One would be hard pressed to explain
his results in any other way, but there was no known mechanism by which RNA
could be transcribed into DNA--so science was very reticent to embrace his
model. In the early 70's, here at the UW, Howard demonstrated the existence
of the enzyme, reverse transcriptase, which was responsible for this unusual
activity of retroviruses. Howard happened to tell DAvid Baltimore about his
idea for testing whehter reverse transcription could be due to a viral
enzyme, and Baltimore spent a couple of weeks in his own lab at MIT doing
the experiment. Both, Temin and Baltimore published similar data around the
same time and, in 1975, shared a Nobel prize for their work--work that Temin
had toiled at for a decade, and Baltimore had tinkered at for a couple of weeks.
This shows that even in the face of strong, albeit circumstantial data,
scientific paradigms are hard to change. It takes compelling data to
overturn dogmas--simply pointing out inconsistencies to the dogma is not
sufficient to change it. Given that the community of science was so
reluctant to embrace Howard's model of reverse transcription until he could
come up with a mechanism by which occurs, it is perhaps more understandable
why the community so tenaciously clings to the evolution model. Several
other models floated around prior to Darwin's model of evolution by natural
selection. The significant thing that Darwin offered was a plausible
mechanism to drive evolution--natural selection. Then, with the new field
of genetics, the mechanism appeared even more plausible. All the other
models that floated around, but that failed to offer a good explanatory
mechanism, fell by the wayside. Although much of the criticism of evolution
science that we see here is reasonable, the scientific alternatives so far
fail to offer a sufficiently compelling explanatory mechanism, and like the
earlier models, are not strong enough to cause a paradigm shift. In other
words, identifying problems with the current model is not sufficient to
cause a change in the central dogma.
I propose that offering an alternative metaphysical paradigm, such as ID, to
counter the metaphysical naturalism associated with much of science, only
addresses the metaphysical component and is not sufficient to change the
scientific paradigm.
Cheers
steve
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Steven S. Clark, Ph.D. Phone: (608) 263-9137
Associate Professor FAX: (608) 263-4226
Dept. of Human Oncology and email: ssclark@facstaff.wisc.edu
UW Comprehensive Cancer Ctr
University of Wisconsin
Madison, WI 53792
"Philosophers consistently see the method of science before their eyes,
and are irresistibly tempted to ask and answer questions in the way science
does. This tendency...leads the philosopher into complete darkness."
Ludwig Wittgestein, The Blue Book, 1933
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