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3. The direction of RNA synthesis was determined by growing bacteria for a short period of time with

trinucleotides labeled with tritium (³H) on their bases. The structure of RNA looks like :

5' pppNpNpNpNp...N-OH 3' (N = nucleosides; p = phosphates).

Cleavage of RNA by a base occurs after the 3' phosphate. (8 points, 2 each)

A. What products are produced if RNA is digested with a base?

B. The products obtained in Part A can be distinguished by thin layer chromatography. Which of the

products would you expect to be differentially labeled if new nucleotides are added at the 5' end (i.e.,

synthesis is in the 3' to 5' direction)?/nC. Which products would be differentially labeled if RNA is synthesized from the 5' to 3' direction?

D. When the experiment was done the tritium label was found in the spot containing N-OH? In which

direction is RNA synthesized.

Fig: 1

Fig: 2