Question

Which of the following sequences is recognised by restriction enzyme BamH1?
A) 5’- GAATTC -3’
    3’-CTTGAA -5’
B) 5”AAGCTT 3’
    3’TTCGAA 5’
C) 5’GGATCC 3’
    3’CCTAGG 5’
D) 5’CCCAAT 3’
      3’GGGTTA 5’

Answer 1

Hint: Endonucleases are very simply enzymes that cut the double stranded DNA molecule within the helix, while exonucleases will cut bases from free ends of the DNA molecules. Some recognise specific sequences of nucleotides.

Complete answer:
Restriction endonucleases are very important in molecular biology and biotechnology. These enzymes are called restriction endonuclease, because they cut within double stranded sections of DNA at very specific sequences. These sequences are often palindromic in nature. That is, they read exactly the same on both strands in the 5’to 3’direction. Some of these produce sticky ends, where there is a single stranded overlap, while others produce blunt ends.
The correct answer is option C. BamH1 cuts just after the first Guanine from the 5’end on both the strands, giving sticky ends 5’GATCC 3’ . The overhang is 4 bases long.
Option A is incorrect but is very significant. This is the recognition sequence for EcoR1, a type II restriction endonuclease, one of the most popular in use.
Option C is the site for the RE HindIII. This has been isolated from Haemophilus influenzae. Like BamH1 and EcoR1, this also produces sticky ends.
Finally, option D is the restriction site for an endonuclease that produces blunt ends. The enzyme cuts at the third base from ends in the 6 nucleotide recognition sequence.

Hence the correct answer is OPTION(C)

Note: BamH1 is produced from Bacillus liquefaciens H. Restriction enzymes are produced mainly in bacterial cells. One restriction enzyme has so far been isolated from human embryonic tissue and it has been named Hsal.