(i) Restriction enzymes cut DNA into fragments. They cut at specific sites determined by the sequence of bases. Following figure shows the base sequences cut by three restriction enzymes and a section of DNA cut by one of these enzymes. Restriction enzymes DNA Sequence
(a) Identify the restriction enzyme that has cut
the section of DNA shown in figure. i
(b) State the name given to the unpaired base sequences that remain after DNA has been cut by the three restriction enzymes shown in figure.
(ii) Human genes may be cloned by inserting lengths of DNA into bacteria. This may be carried out by inserting the required DNA into a plasmid. Explain how lengths of DNA, cut by restriction enzymes, are inserted into plasmids?
(i) (a) Eco RI
(b) Sticky ends/cohesive ends
(ii) Plasmid is cut with a specific restriction enzyme. DNA and plasmid DNA are mixed together. Piece of DNA to be inserted should have same sticky ends made by cutting with same restriction enzyme, so that after mixing, complementary bases like G to C and A to T pairing can take place. Ligase is then added to join the sticky ends.