Chapter 20 Notes:
DNA Technology
Understanding & Manipulating Genomes
• 1995: sequencing of the first complete genome
(bacteria)
• 2003: sequencing of the Human Genome mostly
completed
• These accomplishments depended on new technology:
– Recombinant DNA: DNA from 2 sources (often 2 species)
are combined in vitro into the same DNA molecule
• Called Genetic engineering: direct manipulation of genes for
practical purposes
 DNA technology has launched
a revolution in the area of:
 BIOTECHNOLOGY: the
use of living organisms or their
components to do practical
tasks
-microorganisms to make
wine/cheese
-selective breeding of
livestock
-production of antibiotics
-agriculture
-criminal law
**Practical goal of biotech =
improvement of human health
and food production
Ch 20 looks at:
1. Main techniques for manipulating DNA
2. How genomes are analyzed & compared
at the DNA level
3. Practical applications of DNA technology
(including social & ethical issues)
“Toolkit” for DNA technology involves:
-DNA vectors
-host organisms
- restriction enzymes
VECTORS = carriers for moving DNA
from test tubes back into cells
-bacterial plasmids (small, circular
DNA molecules that replicate within
bacterial cells)
-viruses
HOST ORGANISMS:
bacteria are commonly
used as hosts in genetic
engineering because:
1) DNA can easily be isolated from
& reintroduced into bacterial cells;
2) bacterial cultures grow quickly,
rapidly replicating any foreign
genes they carry.
RESTRICTION ENZYMES = enzymes that
recognize and cut short, specific nucleotide
sequences (called restriction sites)
-in nature, these enzymes protect the
bacterial cell from other organisms by
cutting up their foreign DNA
Restriction Enzymes (cont.)…
most restriction sequences are symmetrical
in that the same sequence of 4-8
nucleotides is found on both strands, but
run in opposite directions
restriction enzymes usually cut
phosphodiester bonds of both strands in a
staggered manner producing single
stranded “sticky ends”
Restriction Enzymes (cont.)…
“sticky ends” of restriction
fragments are used in the
lab to join DNA pieces
from different sources
(complementary base
pairing)
*RECOMBINANT DNA
unions of different DNA
sources can be made
permanent by adding DNA
ligase enzyme (form
covalent bonds between
bases)