Frontiers of

Genetics

Chapter 13

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

The Human Genome• An organism’s

complete set of genetic material, defined by order of DNA bases is known as its genome

• DNA is thousands of times longer than the diameter of the nucleus

• DNA is able to fit into the nucleus because of an elaborate packing system

The Human Genome Project• 13 year project to sequence the entire

human genome (nucleotide sequence)• Knowing sequence is just the first step,

must then distinguish between non-coding (introns) and coding (exons) regions

• Finally functions of all resulting polypeptides must be determined

• Gene identification is useful in evolutionary research as well as diagnosing , treating and possibly preventing diseases/disorders.

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

Genetically Engineering Insulin

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

Animation – Steps in Cloning a Gene

Inserting a DNA Sample into a Plasmid

Examples of Genetic Engineering

Genetic Manipulation of Plants• Genetic engineering of plants is much easier than

that of animals. – natural transformation system ( Agrobacterium

tumefaciens)– plant tissue can re-differentiate – transformation and regeneration are relatively easy for

many

• The soil bacterium Agrobacterium tumefaciens can infect wounded plant tissue, transferring a large plasmid, the Ti plasmid, containing contains genes for the synthesis of (1) food for the bacterium, and (2) plant hormones.

• This plasmid has been genetically modified ("disarmed") and used to insert a gene that can be used as a selectable marker as well as a gene of interest, such as herbicide resistance, virus tolerance, decreased sensitivity to insects or pathogens.

• DNA can now be delivered into the cells by small, µm-sized tungsten or gold bullets coated with the DNA. The bullets are fired from a device that works similar to a shotgun called a gene gun.

ANIMATION

Cloning

Natural v. Artificial Twinning Animation Cloning Animation

Gel Electrophoresis

RFLP Animation

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.

DNA Fingerprinting Animation

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.

Animation

Prokaryotic Control of Gene Expression

Animation 1 Animation 2

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