Another batch of DNA was treated in a likewise manner, except that nucleotides containing thymine were added instead of adenine. (Avril, 187-94)
When these two samples of DNA were mixed, the complementary "tails" of A- and T-bearing nucleotides became joined by hydrogen bonding. This combined the once separate fragments into long, interconnected chains. DNA ligase was then added to form bonds between the sugar and phosphate groups. The two DNA strands were now one.
It was certainly intriguing that one could now cut up DNA into unpredictable heterogeneous fragments and randomly stitch them back together. However, for further insights into the organization of DNA and its genes -- that is, the determination of precise nucleotide sequencesvery specific nucleases would have to be found. The prevailing opinion was that such specific DNA-cutting capability did not exist in nature.
The only clue to the possibility that more specific nucleases might exist came from observations beginning as early as 1953 that when DNA molecules from E. coli were introduced into another slightly different form of E. coli they seldom functioned genetically. They were quickly broken down into smaller fragments. ...Show more