- Email: [email protected]
Summary of the informal discussion of the session on cytogenetics
Experimental
124
SUMMARY
Cell Research, Suppl. 9, 124-125 (1963)
OF THE INFORMAL DISCUSSION SESSION ON CYTOGENETICS
OF THE
DR HOTCHKISS pointed out that too much emphasis may have been placed on the original genetic material of the gametes and less on the interference and modifications that may occur in the DNA during cellular division and growth beyond the zygote stage. Mechanisms similar to bacterial conjugation, transduction, or transformation may play important roles in somatic aberrations, independent of original genotypic factors. Re-assortment of genetic material of homologous chromosomes in higher organisms may resemble in its effects the entry of foreign DNA into a bacterial cell. The insult on the DNA may occur a considerable period of time preceding the abnormal manifestations observed in the cellular progeny. It should be realized that differences in permeability or penetration of cells to various DNA’s or viruses may play important roles as to what happens to a cell. Nevertheless, two questions remain to be answered: (1) How frequently can we expect to find microbial genetic mechanisms operating in cells of higher forms, particularly in somatic cells? (2) How will we recognize these processes and their occurrence, and, in so doing, how can we help to combat them? Dr Simon stated that breakage and rejoining as a means of combination have been found in several bacterial viruses. Similar mechanisms may operate in animal cells among their chromosomes, such ,as breakage and union of autosomes or sex chromosomes. The question of attachment or incorporation of foreign DNA into animal DNA, as can occur in lysogenization in Dr Swift asked bacterial cells by bacterial viruses, remains unanswered. Dr Bonner what the evidence was in favor of a double code, to which he alluded? Dr Swift asked Dr Bonner whether there is a possibility of the existence of structural non-functioning DNA. Dr Bonner stated that recently observed suppressor manifestations, whose functions point to the existence of newly described functional regions of DNA, point to the possibility that as we examine more and more of the functionality of DNA of chromosomes it may reveal that non-functional DNA is non-existent. The problem of the triple vs. the double code remains at the moment an open question. Dr Heidelberger stated that Ablev in Moscow has studied a series of chemically induced and spontaneous mouse hepatomas and showed that all Experimental
Cell Research, Suppl. 9
Summary of fhe informal discussion of the session on cytogenetics
125
of these tumors carry a specific antigen, which appears to be an a-globulin. He thought at first that the antigen was of tumorous origin, but found, in fact, that it was an embryo-antigen, rather than tumor specific. This appears to be a clear experimental demonstration that information carried in the embryo persists and that the process of carcinogenesis involves a possible deletion of a suppressor, so that the embryonic information becomes evident.
Avery A. Sandberg
Experimental
Cell Research, Suppl. 9
124
SUMMARY
Cell Research, Suppl. 9, 124-125 (1963)
OF THE INFORMAL DISCUSSION SESSION ON CYTOGENETICS
OF THE
DR HOTCHKISS pointed out that too much emphasis may have been placed on the original genetic material of the gametes and less on the interference and modifications that may occur in the DNA during cellular division and growth beyond the zygote stage. Mechanisms similar to bacterial conjugation, transduction, or transformation may play important roles in somatic aberrations, independent of original genotypic factors. Re-assortment of genetic material of homologous chromosomes in higher organisms may resemble in its effects the entry of foreign DNA into a bacterial cell. The insult on the DNA may occur a considerable period of time preceding the abnormal manifestations observed in the cellular progeny. It should be realized that differences in permeability or penetration of cells to various DNA’s or viruses may play important roles as to what happens to a cell. Nevertheless, two questions remain to be answered: (1) How frequently can we expect to find microbial genetic mechanisms operating in cells of higher forms, particularly in somatic cells? (2) How will we recognize these processes and their occurrence, and, in so doing, how can we help to combat them? Dr Simon stated that breakage and rejoining as a means of combination have been found in several bacterial viruses. Similar mechanisms may operate in animal cells among their chromosomes, such ,as breakage and union of autosomes or sex chromosomes. The question of attachment or incorporation of foreign DNA into animal DNA, as can occur in lysogenization in Dr Swift asked bacterial cells by bacterial viruses, remains unanswered. Dr Bonner what the evidence was in favor of a double code, to which he alluded? Dr Swift asked Dr Bonner whether there is a possibility of the existence of structural non-functioning DNA. Dr Bonner stated that recently observed suppressor manifestations, whose functions point to the existence of newly described functional regions of DNA, point to the possibility that as we examine more and more of the functionality of DNA of chromosomes it may reveal that non-functional DNA is non-existent. The problem of the triple vs. the double code remains at the moment an open question. Dr Heidelberger stated that Ablev in Moscow has studied a series of chemically induced and spontaneous mouse hepatomas and showed that all Experimental
Cell Research, Suppl. 9
Summary of fhe informal discussion of the session on cytogenetics
125
of these tumors carry a specific antigen, which appears to be an a-globulin. He thought at first that the antigen was of tumorous origin, but found, in fact, that it was an embryo-antigen, rather than tumor specific. This appears to be a clear experimental demonstration that information carried in the embryo persists and that the process of carcinogenesis involves a possible deletion of a suppressor, so that the embryonic information becomes evident.
Avery A. Sandberg
Experimental
Cell Research, Suppl. 9