Mammalian cells growing in culture were labeled with [3H]-thymidineto estimate the rate of DNA synthesis. The thymidine administered had aspecific activity of 3000 cpm/pmol. At intervals, samples of culture weretaken and acidified to precipitate nucleic acids. The rate of incorporation ofisotope into DNA was 1500 cpm/106 cells /min. A portion of culture wastaken to determine the specific activity of the intracellular dTTP pool, whichwas 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 ofthymine nucleotides incorporated into DNA?(c) How could you determine the specific activity of the dTTP pool?
Mammalian cells growing in culture were labeled with [3H]-thymidine
to estimate the rate of DNA synthesis. The thymidine administered had a
specific activity of 3000 cpm/pmol. At intervals, samples of culture were
taken and acidified to precipitate
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
(c) How could you determine the specific activity of the dTTP pool?
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