DNA renaturation curves occasionally show three distinct phases of renaturation. In this graph, DNA renaturation is plotted against "C0t" (initial concentration times time of renaturation-essentially a measure of relative renaturation time). See Figure 21.4.
(a) Identify each part of this plot that corresponds to reannealing of
(1) Unique sequences,
(2) Moderately repetitive sequences,
(3) Highly repetitive sequences.
(b) Suppose that you cloned a single-copy gene, such as the gene for dihydrofolate reductase (DHFR), into a plasmid vector and subjected it to renaturation analysis. Sketch the curve you might expect.
(c) Suppose that you used reverse transcriptase (Chapter 24) to copy the ovalbumin mRNA and cloned this complementary DNA (cDNA) into a plasmid vector. Would you expect this cDNA to reanneal
(1) More slowly,
(2) More rapidly,
(3) At the same rate as genomic DNA? Briefly explain your answer.

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