1990 Fiscal Year Final Research Report Summary
Analysis of DNA Sequence Changes in Radiation-Induced Mutations.
| Project/Area Number |
01480533
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
放射線5生物学
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| Research Institution | Kyoto University |
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Principal Investigator |
IKENAGA Mituo Kyoto Univ., Radiat. Biol. Ctr., Professor, 放射線生物研究センター, 教授 (70025378)
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| Co-Investigator(Kenkyū-buntansha) |
TAKIMOTO Koichi Yamaguchi Uviv., Dept. Agriculture, Associate Professor, 農学部, 助教授 (00115875)
ISHIZAKI Kanji Kyoto Univ., Radiat. Biol. Ctr., Associate Professor, 放射線生物研究センター, 助教授 (70111987)
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| Project Period (FY) |
1989 – 1990
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| Keywords | X-ray-induced mutations / E. coli crp gene / DNA sequencing / Base substitution / hot spot / N-methyl-N'-nitro-N-nitrosoguanidine |
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| Research Abstract |
Plasmid DNA carrying the adenosine 3', 5'-cyclic monophosphate receptor protein (crp) gene of Escherichia coli was irradiated with X-rays, and the mutations produced in the crp gene were assayed by transforming the recipient E. coli cells. Ninety-six mutant clones were isolated, and mutational changes were determined by DNA sequencing. Of the 92 mutations thus detected, 74 represented base substitution mutations and the remaining 18 were frameshifts. The base substitutions included 56 G : C to A : T transitions, 10 G : C to T : A transversions and 7 G : C transversions. An A : T to G : C transition was found only once, and neither an A : T to T : A nor an A : T to C : G transversion was detected. The frameshift mutations consisted of 11 one-base deletions and 7 one-base insertions. Accordingly, a G : C to A : T transition was the most predominant type of mutation, which constituted 76% (56/74) of the total base substitutions and 60% (56/92) of all detected mutations. Furthermore, of the 56 transitions, about three-quarters (41 clones) clustered at an identical site, a cytosine residue at the 706 position, demoustrating that this site is a distinct hot for X-ary mutagenesis. These rsults raise the possibility that radiation induced mutations may not necessarily occur randomly, at least in certain cases.
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