Question

a bacterium with heavy strands is allowed to replicate in non radioactive growth media for three generations.what will be the percentage of bacteria that contains non-radioactive DNA? Explain

Answer 1

Dear student,
75% of the bacterium will be labelled with non radioactive DNA and 25% of the bacterium will be labelled with one heavy strand of DNA and one light strand of DNA.
Initially both the strand of DNA is radioactive. In first generation two bacteria will be formed both containing hybrid strands i.e one heavy strand and one light strand. In second generation four bacteria will be formed in which 50% is labelled with non radioactive DNA and 50% is hybrid containing both radioactive and nonradioactive strands. In third generation out of eight bacterium produced six of them are labelled with non radioactive DNA and two of them are hybrid. Therefore we can say that 75% of DNA is non radioactive while 25% are radioactively labelled.

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