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.