마우스 암세포 DNA의 반복염기서열구조

Abstract

The kinetics of reassociation of the DNA of mouse tumor cells has been examined to determine the amount and repetition frequency of various DNA fractions. Before the reassociation experiment the purity of DNA preparations was confirmed by its melting behavior(temperature denaturation). The Guanine-Cytosine content of DNA was also calculated from the melting curve. (Trn value) The transplantable tumor used in the denaturation experiment were Ehrlich ascites tumor, Sarcoma 180, Yun salivary adenocarcinoma and Yun liposarcoma. Among 4 kinds of mouse tumors, Ehrlich ascites tumor and Yun salivary adenocarcinoma were used in the reassociation experiment. The results were analyzed by comparing the pooled DNA of normal liver cells with that of tumor cells. The following results were obtained; 1. The Guanine-Cytosine contents of each DNA are as follows. Ehrlich ascites tumor 41. 5%(Tm: 86. 3°C) Sarcoma 180 41. O%(Tm: 86. 1°C) Yun salivary adenocarcinoma 39.5%(Tm: 85. 5°C) Yun liposarcoma 40.0%Cfm: 85. 7°C) normal liver cell 41. O%(Tm: 86. 1°C) 2. The amount of non-repetitive DNA of the tumor cells decreased by about 15 percent, compared with that of normal liver cell DNA. 3. There are great differences of amount and repetitive frequency between normal and tumor cell DNA, especially in the intermediate repetitive fraction. The amount of highly repetitive DNAs of tumor cells is increased 2~5% over that of normal cell DNA. In the case of the intermediate fraction, its amount in the tumor cells is approximately twice that of normal cells. In addition to the increase in amount of repetitive sequences, the frequency of repetition is also increased in both fractions of each tumors. The average nucleotide repetition length in the intermediate fraction of the tumor cell DNA is approximately half that of the correspondng length in the normal cell DNA fraction