"Nucleic Acids"

Date:
1959
Reference:
PP/CRI/E/1/7/1
Catalogue details

Licence: In copyright

Credit: "Nucleic Acids". Source: Wellcome Collection.

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    It is Important to notice two points about the DNA structure. (1) the two chains are helically wound around one another and cannot be separated merely by translating them sideways, (2) the two chains run in opposite directions. That is* if fee put an arrow on a chain depending upon the di rection of the sequence of chemical atoms in its back bone, then if the arrow on one chain points up, that on the other chain will point down. These points are both rather important in considering detailed schemes for MA replication. 1 shall leave Dr. Macloed to detail the evidence we have that DNA is an important part of the genetic material. In brief whenever we find genetic material we find DMA (except for certain small viruses which contain RNA), and we find it nowhere else* with minor importarti exceptions. It appears to be very stable metabolically, as one might expect for a genetic substance, and there is a constant amount per chromosome set in a given organism no matter which of its cells we examine. Thus DNA is heavily implicated by circumstantial evidence. Is there direct evidence that DNA contains genetic information? The best example is that of transforming factor, which Dr. Macloed will discuss. The next best that of bacterial viruses which attack E. Coli, known as the T-even bacteriophages» that is T g , T^ and Tg. These .viruses