The given picture was obtained from an agarose gel electrophoresis of a plasmid after digestion with restriction enzymes either $\mathrm{X}, \mathrm{Y}$ or both X and Y.

Which one of the following diagrams correctly represents the position of the restriction enzyme sites $(\mathrm{X}, \mathrm{Y})$ on the 10,000 bp plasmid?

Which of the following plasmid vectors can be used for cloning of a gene, with restriction enzymes BamHI and EcoRI, and ampicillin-containing nutrient agar for selection? [Ori - origin of replication; $\mathrm{Amp}^R$ - gene for ampicillin resistance]

Polymerase chain reaction (PCR) is used to amplify a gene of interest (GOI). If, after 30 cycles of PCR, 1 billion copies of GOI are produced, approximately how many copies of GOI were present at the end of the $20^{\text {th }}$ cycle?

A 1000 base-pair DNA fragment was cloned between Hind III and EcoRI sites of the plasmid vector (plAT) of size 3500 base-pair. The cloned fragment had a Not I site as shown in the figure. In order to confirm the presence of the insert, the recombinant plasmid was digested completely with (a) Not I and EcoR I, and (b) Not I and Hind III.

In lane 1 the products of the digestion by Not I and EcoRI was loaded. In lane 2 the products of the digestion by Not I and Hind III was loaded. Which one of the following correctly represents the agarose gel electrophoresis profile of the digested recombinant plasmid for (a) and (b), respectively?