Video Transcript
Some restriction enzymes recognize
a section of DNA that is the same sequence read five prime to three prime on one
strand as it is read five prime to three prime on the complementary strand. An example of this is shown in the
diagram. What term is given to this
pattern?
This question asks us about
restriction enzymes. Let’s review what restriction
enzymes are and how they can be used to manipulate DNA.
Restriction enzymes are useful
tools in biotechnology because they can be used to cut specific DNA sequences so
they can be combined in interesting ways. They were originally discovered in
bacteria as a way for bacteria to defend themselves against viral infection. Restriction enzymes can cut viral
DNA into pieces so the virus is restricted in carrying out its lifecycle.
There are many different
restriction enzymes, and each has its own target DNA sequence that it recognizes and
cuts. This is called a recognition
sequence. These recognition sequences are
palindromes, meaning they’re read the same way forwards and backwards. The word racecar is an example of a
palindrome because it reads racecar whether we read it in one direction or the
other.
The provided diagram is the
recognition sequence for a restriction enzyme and is a palindrome. Reading the sequence in the five
prime to three prime direction on the top strand, we see it’s GAATTC. And if we look at the opposite
strand and read it in reverse, we still get GAATTC. So when we’re talking about
palindromes in DNA, the sequence on the five prime to three prime strand is the same
as the sequence on the complementary strand when read in the five prime to three
prime direction. So if we go back to our question,
this term refers to a palindrome.
