Restriction Enzymes & Sticky Ends — NEET Biology
📚 Practice ConceptIn 1966, Boyer took over assistant professorship at the University of California at San Francisco. By 1969, he performed studies on a couple of restriction enzymes of the E. coli bacterium with especially useful properties. Boyer observed that these enzymes have the capability of cutting DNA strands in a particular fashion, which left what has become known as 'sticky ends' on the strands. These clipped ends made pasting together pieces of DNA a precise exercise.
Which of the following statements about restriction enzymes and the DNA fragments they generate are NOT correct? S1: Restriction enzymes always cut DNA molecules at the exact center of palindromic recognition sequences. S2: Sticky ends are single-stranded overhangs that readily form hydrogen bonds with complementary sequences. S3: The formation of recombinant DNA molecules requires cutting both the vector and the alien DNA with different restriction enzymes to ensure specific ligation. S4: The stickiness of DNA ends facilitates the action of DNA ligase by directly promoting stable covalent bond formation between the sugar-phosphate backbones. S5: Exonucleases remove nucleotides from the ends of DNA, while endonucleases make cuts at specific positions within the DNA.
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