In Figure 2A the authors are using a transcriptional pulse chase to trap mRNA degradation intermediates. They use a galactose inducible promoter to initiate new mRNA synthesis in the presence of radiolabeled nucleotides (the pu)se). After 10 minutes (when the mRNA synthesis is complete) they remove the radiolabeled nucleotides and monitor degradation products of the newly synthesized radiolabeled mRNA (the chase). The polyG sequence is inserted at te the BgIII site A poAfion 28 (1328pGtv1). The pC marks the poly C sequence in the probe. There are 2 polyC sequences one at position 28 which can hybridize with the poly G and another at an internal location which does not have a complementary polyG sequence to hybridize to. The authors suggest that mRNA degradation begins from the 5' end. Provide a rationale for whether or not you are convinced.
DRAW how the result would be if degradation were occurring from the 3 end (rather than from the 5' end as the paper demonstrated). Model your figure after Figure 2 in the paper and on your figure:
(1) mark where the pG site should be, (2) what should the probe look like? (3) mark where the hypothetical bands would run? (4) draw a cartoon of what the band represents.
Sample Solution