Why are those restriction enzymes which cut the DNA strands a little away from the centre of the recognition sequence more useful in the construction of recombinant DNA?


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  • $\begingroup$ Why do you think? What would be the use of overhanging (hint: sticky) ends vs a blunt cut? $\endgroup$ – MattDMo Oct 26 '16 at 14:12
  • $\begingroup$ I've read this and there should be and is a reason behind it $\endgroup$ – user26857 Oct 26 '16 at 14:13
  • $\begingroup$ Yes, there is, and I'm trying to help you answer your own question. So, we're constructing recombinant DNA, which means we're splicing a linear piece of double-stranded DNA into a spot (most likely) in a plasmid. Why would you want sticky ends, and where would you want them? $\endgroup$ – MattDMo Oct 26 '16 at 14:18
  • $\begingroup$ Also important - would you want the same sticky ends everywhere, or only certain places? $\endgroup$ – MattDMo Oct 26 '16 at 14:19
  • $\begingroup$ I'm Confused***** $\endgroup$ – user26857 Oct 26 '16 at 14:22

There is two main ways to cut DNA, creating Blunt ends or Sticky ends.

Blunt end example of SmaI recognition site: ("|" is the cutting site)

5'---CCC | GGG---3'

3'---GGG | CCC---5'

Sticky end example of EcoRI recognition site:

5'---G | AATTC---3'

3'---CTTAA | G---5'

In blunt end example, the only way you can attach both pieces of DNA is one after the other, which is harder to do and not specific at all since any bases can go one after the other.

5'---CCC --> <-- GGG---3'

3'---GGG --> <-- CCC---5'

In the sticky example, the sequences will recognize its homologous sequence and attach to it (The TGGG will attach to the ACCC part, making a strong bond). When attaching one strand of DNA on the other, the bases must be homologous (A-T, G-C), this gives specificity since the strand can only be attached with specific sequences.



Here is some good references on restriction enzymes:

  1. Wikipedia(Complete informations with strong references)
  2. Biotech Learning Hub (Basics easily understandable)

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