Mammalian cells growing in culture were labeled with 3H thymidine to estimate the rate of DNA synthesis Te thymidine administered had a specic activity of 3000 cpm pmol At intervals, samples of culture were taken and acidied to precipitate nucleic acids Te rate of incorporation of isotope into DNA ...

a b 1500 cpm dTTP incorporated per minute per 10 6 cells corrected for the 20 fraction calcula ...

Mammalian cells growing in culture were labeled with [3H]-thymidine to estimate the rate of DNA synthesis. Te

Question:

Mammalian cells growing in culture were labeled with [3H]-thymidine to estimate the rate of DNA synthesis. Te thymidine administered had a speciﬁc activity of 3000 cpm / pmol. At intervals, samples of culture were taken and acidiﬁed to precipitate nucleic acids. Te rate of incorporation of isotope into DNA was 1500 cpm / 106 cells / min. A portion of culture was taken to determine the speciﬁc activity of the intracellular dTTP pool, which was found to be 600 cpm / pmol.
(a) What fraction of the intracellular dTTP is synthesized from the exogenous precursor?
(b) What is the rate of DNA synthesis, in molecules per minute per cell of thymine nucleotides incorporated into DNA?
(c) How could you determine the speciﬁc activity of the dTTP pool?