INFLUENCE OF DNA SYNTHESIS ON THE PRODUCTION OF CHROMATID ABERRATIONS BY X RAYS AND MALEIC HYDRAZIDE IN VICIA FABA

Journal Article · Wed Jan 01 04:00:00 EST 1964 · Genetics (U.S.)

OSTI ID:4113416

Evans, H J; Scott, D

Using H/sup 3/-thymidine as a marker for DNA synthesis, and autoradiographic techniques, the average durations of the various parameters of the mitotic cycle in Vicia roots were determined as follows: presynthesis phase (G/sub 1/) 4.9 hr, DNA synthesis phase (S) 7.5 hr, postsynthesis phase (G/sub 2/) 4.9 hr, and mitosis (M) 2 hr. The duration of these phases and their sensitivity to the production of chromosome aberrations following x ray or maleic hydrazide (MH) treatment was then studied in experiments using combined treatments with these agents and with H/sup 3/-thymidine. Cells exposed to 100 rads of x rays whilst in G/sub 2/ were delayed in development and contained chromatid-type aberrations. The aberration yield was highest in cells exposed whilst in mid-G/ sub 2/, cells in late S and early and late G/sub 2/ being less sensitive. In contrast with the x ray results, with MH it was found that G/sub 2/ cells were not delayed in their development to the first mitosis and did not contain any aberrations. However, these cells contained chromatid-type aberrations when observed at the second posttreatment mitosis. Cells exposed to MH whilst in the S phase were considerably retarded in development and carried chromatid-type aberrations at the first and later posttreatment mitoses. The yield of aberrations in these cells was found to be directly correlated with the amount and rate of DNA synthesis occurring during exposure. No chromosome-type aberrations were induced by MH; cells in G/sub 1/ were sensitive but contained only chromatid-type changes. It was concluded that the aberrations induced by MH are consequences of errors in chromosome duplication occurring only during the DNA synthesis phase, and possible mechanisms of action are discussed. Comparisons were made between the relative frequencies of the various chromatid aberration types after x rays and MH and it was concluded that the reduced frequency of translocation following chemical treatment was a consequence of the dependence of aberration formation on duplication. The absence of chromosome- type breaks and delayed production of aberrations with MH in Vicia parallels some of the effects of other chemical agents which produce structural changes and mutations in Drosophila. These parallels are discussed, particularly with reference to the production of mosaic individuals. (auth)

• Research Organization: Medical Research Council Radiobiological Research Unit, Harwell, Berks, Eng.
• NSA Number: NSA-18-008158
• OSTI ID: 4113416
• Journal Information: Genetics (U.S.), Journal Name: Genetics (U.S.) Vol. Vol: 49; ISSN GENTA
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

BIOLOGY AND MEDICINE
CHEMICALS
CHROMATIDS
CHROMOSOMES
DNA
DROSOPHILA
HYDRAZIDES
INSECTS
LABELLED COMPOUNDS
MALEIC ACID
METABOLISM
MITOSIS
MUTATIONS
NUCLEIC ACIDS
PLANTS
QUANTITY RATIO
RADIATION DOSES
RADIATION EFFECTS
RADIOAUTOGRAPHY
RADIOSENSITIVITY
ROOTS
TRITIUM
VARIATIONS
VICIA
X RADIATION