[Discussion transcription]

Date:
[c. 1956]
Reference:
PP/CRI/H/2/15
Catalogue details

Licence: In copyright

Credit: [Discussion transcription]. Source: Wellcome Collection.

    19/48
    the two strands do not come apart - that is, in which the two original struc tures were held together in some way. As replication occurs in this loop, the loop moves down along the strands* supplying the information to the entire now structure. All our present experiment indicates is that at least once in most cases in the roughly $ generations of growth which must take place in the bacteriophage cycle there has been at least one of this type of replication, but it doesn't by any means imply that every replication is of this type. The reason I mention this is the fact that there are experiments which we are now carrying out which seem encouraging in answering this question. We can extract the DNA from bacteria after labelling them, transferring them to a cold medium, and allowing them to grow for exactly one, two, or three generations, even for instance in synchronized cultures, and find out whether the radioactivity in a single DNA molecule doesn't in fact drop by a factor of 2 in the first generation and not thereafter. However, this is only to indicate to you things which are by no means proven by these experiments. BROWNs By combining these astronomical methods of Dr. Leventhal with the more plebian methods of fractionation we have been able to get some chemical ini or- mation about these big pieces in the bacteriophage DNA. Our original frac tionation method was that by combining fractionated hist one with cellulose by diazotozation and then by adsorbing the nucleic acid on the cellulose histone and then eluting with sodium chloride we obtained elution patterns showing two large peaks. We determined the base ratios in the elution diagram. The ratio was adenine * thymine The base ratios in the different guanine + 5-hydroxymethyl cyt osine fractions turned out to be slightly different. In one case fraction A was 1.9 and fraction B was 2.1. Then we measured the glucose content by reacting these fractions with an throne, and we found the amount of glucose in fraction A to be molecularly equivalent to about 6of the 5-hydroxymethyl cytosine. In the case of fraction B we found a 100$ equivalence of glucose to 5-hydroxymethyl cytosine. With Dr. Neville Simons we have examined these. We put osmotically shocked hot phage on these columns and then examined the