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)