Playing god for fun and profit!
What happens when a mummy test tube and
a daddy test tube love each other very much.
What is Recombinant DNA?
• DNA from one organism that has had DNA
from another organism inserted in it. It
may be from a different species.
• Really it is just cut and paste job using
chemicals instead of scissors and glue.
• The scissors are Restriction enzymes.
• The glue is called DNA Ligase.
The Scissors: Restriction Enzymes
• Restriction Enzymes are enzymes that cut
DNA at a specific sequences of bases.
• Some will make a straight cut so the cut
ends of the DNA are even in length.
• Others will make a jagged cut with one
strand longer than the other; this is known
as a “sticky end”.
EcoRI digestion produces "sticky" ends,
whereas SmaI restriction enzyme
cleavage produces "blunt" ends
The Glue: DNA Ligase
• DNA ligase is used to glue the cut ends of
• Works with both sticky and blunt ends but
sticky ends produce a better yield.
• Why would you use blunt ends?
Let’s see the cutting and pasting
process in full:
• Once you have created your recombinant DNA
you then have to find a way to stick it inside your
• How you do this will depend on:
– What organism you want to put it in.
– Whether you want the genetic change to be
– If you want the change to be pass on the offspring
– How precisely you want to place the DNA in the
– Bacteria naturally have small circles of DNA
with genes on them (these is different from
their main chromosomal DNA) that they may
pass between themselves.
– Recombinant plasmids, as seen in a previous
slide can be put into bacteria to give them
– They may be inserted into bacteria using
• Viral vectors
• Yeast artificial chromosomes.
• Gene guns
Identifying Cells with Recombinant
• In bacteria:
– add antibiotics resistance genes to the recombinant
– add a marker gene that causes a colour change.
• Use antibodies to detect protein of inserted gene.
• Complementary RNA or DNA probes (these are
probes that have DNA that is complementary to
your inserted genes that have a marker (e.g.
florescent dye) on them).