3. DNA synthesis on the lagging strand in E. coli is a complex process known to involve several proteins. Initiation of a new chain is catalyzed by the enzyme (a)_________ , and elongation is catalyzed by the enzyme (b)_________ Synthesis is discontinuous, yielding short segments called (c)_________ , which are eventually joined by the enzyme (d)_________ ， which requires the cofactor (e)_________ . (5%)

2. In Figure below, the bacterial activator protein CAP and the Lac repressor have been placed in the four possible combinations on their binding sites in the promoter for the Lac operon. Each combination of gene regulatory proteins corresponds to a particular mixture of glucose and lactose. For each of the four combinations, indicate on the left-hand side of the figure which sugars must be present and, on the right-hand side (a-d), whether the operon is expected to be turned ON or OFF. (4%)

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