Biotechnology

DNA technology

Review

Some of the most important techniques used in biotechnology involve making recombinant DNA molecules

Recombinant objects have been reassembled from parts taken from more than one source Bicycles

Recombinant DNA

Your genome is recombinant in that part of it came from your mother and part of it came from your father

Recombinant DNA molecules are pieces of DNA that have been reassembled from pieces taken from more than one source of DNA

Often one of the sources is a Plasmid

Plasmids Small circular DNA molecules that

can reside in cells. Often contain genes fro resistance

to antibiotics. They can spread antibiotic

resistance They are also used for human

benefit.

Genetic Engineering

Possible because of special enzymes that cut DNA

These enzymes are called RESTRICTION ENZYMES

DNA Scissors: An Introduction to Restriction Enzymes

Restriction enzymes, are proteins that recognize and bind to specific DNA sequences and cut the DNA at or near the recognition site.

A nuclease is any enzyme that cuts the phosphodiester bonds of the DNA backbone, and an endonuclease is an enzyme that cuts some where within a DNA molecule.

Restriction enzymes were originally discovered through their ability to

break down, or restrict, foreign DNA. can distinguish between the DNA normally present

in the cell and foreign DNA, such as infecting bacteria virus DNA

The enzymes defend the cell from invasion by cutting the foreign DNA into pieces, rendering the DNA nonfunctional.

Restriction enzymes appear to be made exclusively by prokaryotes.

Restriction enzymes

generally recognize specific DNA sequences of 4 to 6 base pairs.

These recognition sites are a palindrome in that the 5’ 3' base sequence is the same on both strands.

Most of the enzymes make a cut in the phosphodiester backbone of DNA at a specific position within the recognition site, resulting in a break in the DNA.

These recognition cleave sites are called restriction sites.

Restriction Enzymes

Recognize and cut at specific places along the DNA molecule called restriction sites.

Each different restriction enzyme has its own type of site.

Restriction site is a 4 or 6 base pair sequence that is a palindrome.

A DNA palidrome is a sequence in which the “top strand read from left to right is the same as the bottom strand read from right to left.