Question

Which of the following portions of a longer duplex DNA segment are likely to be recognition sequence of a restriction enzyme?

• A. 5'-AGTC- 3'3'-TCAG- 5'
• B. 5'-ATCG- 3'
  3'-TAGC- 5'
• C. 5'-ACCT- 3'3'-TGGA- 5'
• D. 5'-ACGT- 3'3'-TGCA- 5'

Answer 1

The correct option is D

5'-ACGT- 3'

3'-TGCA- 5'

The restriction enzymes recognizes the pallindromic sequence. As against a word-palindrome where the same word is read in both directions, the palindrome in DNA is a sequence of base pairs that reads same on the two strands when orientation of reading is kept same. For example the sequence in option D. Restriction enzymes cut the strand of DNA a little away from the centre of the palindrome sites, but between the same two bases on the opposite strands.