GENETIC ENGINEERING
RESTRICTION ENZYMES Also called restriction endonucleases Proteins produced by bacteria as a
defense against “foreign” DNAServe as bacteria’s “immune system”
RESTRICTION SITES Specific sequences of DNA that certain
restriction enzymes recognizeExamples:
EcoRI cuts at DNA sequence GAATTC CTTAAG
The arrows point to the cut sites in the DNA sequence
Hydrogen bonds between the nitrogen bases fall apart after the cuts are made
Restriction sites leave “sticky ends” because little tails are left making it easier for the complementary ends to rejoin
More examplesAluI cuts at DNA base sequence AG
CT TC GA
Do these cut ends leave sticky ends?
NO! When the restriction enzymes cut
the two DNA strands directly across from one another they produce “blunt ends”.
SIGNIFICANCE OF RESTRICTION ENZYMES Because all living things have DNA
that shares the same basic structure we can use bacterial restriction enzymes to “cut” DNA in any organism and insert desired genes
Enzymes called ligases stick the new bonds together creating a segment of DNA that contains new genes.
New DNA is called recombinant DNA
REAL LIFE BENEFITS Production of insulin by bacteria cells to
create supplies of insulin for diabetics. Transgenic corn that has been inserted
with a gene that makes it more resistant to pests
Many more!! Assignment: Find two real life uses of
restriction enzymes in genetic engineering. Bring your articles in and be prepared for a discussion on Monday.