C. Crick, visiting professor of explained his latest genetics to a spellbound, overflow of more than 400 at yesterday. Crick and J.D. Watson Professor of Biology, are the of the Watson-Crick model of acid DNA, considered one outstanding achievements of .

at the University of experiments were devoted to the ultimate genetic . The ordering of bases in nucleic the ordering of amino proteins, the principal living matter.

said his work indicates that it of three bases--the code-- acid that determine amino if the four kinds of bases in RNA are represented by the A, B, C, and D, ABC may result of one amino acid, ACB . The nucleic acid chain which these two amino acids can as ABC-ACB.

Arranged From One Point

must be arranged in proper three starting from a on the chain, Crick said, to the amino acids. In other words, base A is removed from the ABC-ACB, the chain now begins and neither amino acid will be But in some cases, Crick stated, of a base at one point on may compensate for the a base at another.

the defective chain BCA-CB. B is inserted between BC, ACB in the new chair BBC-ACB. second amino acid would be as before, although base A moved from the original chain The expected mutation--that acid would be formed-- "suppressed," Crick said.

Certain groups of three bases may not determine an amino acid. If in the original chain ABC was such a "nonsense group," the change to BBC in the new chain will not affect the formation of the protein, Crick pointed out. Thus restoring the second group ACB restores the protein.

Actually this description is oversimplified. Crick said, for he feels that more than one group of three bases is necessary to determine an amino acid. Thus while there are only 20 amino acids, there may be more than 50 "sense" triplet groups of bases, groups which influence amino-acid formation.

Most geneticists hold this view, Crick stated, but many biochemists disagree, claiming that there are fewer than 30 "sense" triplet groups.

Crick's experiments involved the nucleic acid of bacteriophage, cells which destroy bacteria. Each "phage" will only lyse specific bacteria. Changes in genetic structure in the phage can therefore be observed in the failure of the phage to exist on its specific bacteria.

At the beginning of his lecture Crick pointed out that geneticists in the past had been extremely reluctant to give up mistaken ideas. "I've often wondered what would happen," he said, "if the gene turned out to be polysaccharide."