DNATechnology

Chapter 12

Applications of Biotechnology

• Biotechnology: The use of organisms to perform practical tasks for human use. – DNA Technology: Application of biotechnology

in which genomes of organisms are analyzed and manipulated at the molecular level

• Bacteria, such as E. coli, serve as useful models for gene manipulations– Do not undergo meiosis (reproduce asexually)– Still have means of genetic recombination

• This natural recombination process is capitalized on in current DNA technology procedures

Selective Breeding• Cross-breed organisms with desired

traits– Enhance expression of trait– Produce combination of desired traits

Lederberg & Tatum’s Experiment

Recombinant DNA Technology• Combine genes from different sources, even

different species, into a single DNA molecule• Bacteria have small circular pieces of DNA called

plasmids separate from their larger single chromosome

• Plasmids can replicate and pass between bacterial cells allowing gene sharing – associated with antibacterial resistance

Genetic Engineering• Plasmids are used to

add genes for useful products into bacteria through a process called gene cloning– Remove plasmid– Add useful gene– Reinsert in bacteria

where genes are copied many times

Genetically Engineering Insulin

Gene Cloning

How can we do this?• Restriction enzymes are proteins that cut genes at specific DNA

sequences.• Over 75 different kinds of restriction enzymes are known; each one

“recognizes” and cut DNA at a particular sequence• Restriction enzymes allow DNA to be cut into fragments that can be

isolated, separated, and analyzed.• The cut ends produce matching “sticky ends” on the DNA fragment and

the cut plasmids.

Restriction Enzyme Action & Cloning into a Plasmid

Inserting a DNA Sample into a Plasmid

Reverse Transcriptase & Gene Cloning

Cloning

Gel Electrophoresis

http://learn.genetics.utah.edu/content/labs/gel/

Restriction Sites

Layout of an Electrophoresis Gel

Loading the Wells of a Gel

Uses of Electrophoresis• Isolation of DNA fragments so that they can

be incorporated into a plasmids or some other vector. 

• Creating a DNA map so that we know the exact order of the nucleic acid base pairs (A, T, C, or G) along a DNA strand.

• Perform DNA Fingerprinting, which can be used to test organic items, such as hair or blood, and match them with the person that they came from.  This is useful in criminal investigations.

Polymerase Chain ReactionMethod of photocopying DNA in vitro to provide large supply to avoid needing large sample size of cells to extract it (DNA) from.

Prokaryotic Control of Gene Expression

Eukarotic Controls of Gene Expression

• Gene expression is the transcription and translation of genes into proteins

• Eukaryotic controls are elaborate than prokaryotes

• Genes are not controlled in clusters

• Proteins called transcription factors regulate transcription by binding to promoters or RNA polymerase– Turned ON or OFF by

chemical signals in the cell

Cellular Differentiation

STEM CELLS are cells that are undifferentiated and have the potential to differentiate into various types of cells

Homeotic Genes

• “Master switches”; control formation of body parts in specific locations

• Small changes in these genes can result in major morphological changes