Biotechnology:How Do We Use What We Know

about Life?

Role of bacteria in technology

• Advantage to using bacteria– Possess plasmids

• Small extra loops of DNA

– Experience transformation• Bacteria take up plasmids from surroundings

Role of bacteria in technology

• Advantage to using bacteria:

– Scientists can genetically engineer plasmids by inserting gene of interest into bacterial plasmid.

Gene Cloning• Definition: using bacteria to make multiple

identical copies of a single stretch of DNA.• Useful in understanding eukaryotic genome.• Cloning Vector:

– Any vehicle that inserts a fragment of foreign DNA into the genome of a host cell.

– Example: virus or genetically engineered plasmid.

– Used in gene therapy.

Genetic Engineering

• Definition: Ability to precisely manipulate DNA sequences from widely different organisms.

• Process requires– Ability to cut DNA– To insert foreign DNA

segment– “Glue” DNA sequences

together

Molecular Scissors

• Restriction enzymes:– Cut DNA at specific places called recognition sites.– Form “sticky ends.”

Restriction Sites

Molecular Paste• DNA Ligase:

– Form bonds between the sugar and phosphate backbone of the DNA molecule.

• Restriction enzymes and DNA ligase make possible the combination of DNA from different organisms into one DNA molecule– Called recombinant DNA

Making Recombinant DNA

How do we know what size DNA fragments we have?

• Agarose gel electrophoresis:– Allows separation of

DNA on the basis of size.

– Can visualize DNA to determine exactly how large it is.

Making a DNA library• Need the following:

– A gene of interest– Restriction enzymes– Plasmids– DNA ligase

• Can create a cloning vector using these tools which can be inserted in a bacteria

• Allow bacteria to reproduce• DNA library: entire collection of bacterial

cells which contain cloned gene

Screening a DNA Library

• Need to find the gene of interest in the bacteria or bacterial cells that possess the gene of interest.

• Use nucleic acid hybridization to find the gene of interest.

Nucleic Acid Hybridization

• Requires a molecular probe:– Probe is made of a synthetic single-stranded

DNA whose sequence is complementary to the gene of interest.

– Also has a built-in marker so scientists can find it.

• When probe binds to denatured gene of interest, a hybrid is formed.

Polymerase Chain Reaction• Allows scientists to make copies of a small

sample of DNA.• Requires:

– Primers: two synthetic short strands of DNA that are complementary to each of the two DNA sequences that flank the gene or DNA to be copied.

– Heat-resistant DNA polymerase– Nucleotides

DNA Sequencing

• Determining the base-by-base order of the nucleotides in a stretch of DNA.

• Can help us identify regions of DNA that contain genes.

DNA Sequencing• Makes possible comparisons of DNA

sequences– between individuals to teach us about our

susceptibility to disease.– between species to teach us about how we

evolved.• Also, DNA sequences teach us about the

regulation of gene expression.

Human Genome Project (HGP)

• Overall goal: – decipher the full set

of genetic instructions in human DNA.

– Develop a set of instructions as a research tool for scientists.

Human Genome Project (HGP)

• Several genomes of model organisms have been sequenced as a part of the project.

What We Have Learned From Human Genome

• First lesson:Human DNA consists of 3 billion base pairs– Contain 20,000-25,000 genes

• 2-3 times as many genes as a worm or fruit fly.

• Approximately 3% of DNA contains the information to make proteins.

What We Have Learned From Human Genome

• Second lesson: a greater understanding of genes themselves. – Has important implications to understanding

human biology and what goes wrong in disease states.

– Help us define disease states and predict possible candidates who are likely to suffer from a disease based on their nucleotide sequences.

What We Have Learned From Human Genome

• Third lesson: lessons about the human family; both our diversity and evolution.– Compare base-by-base sequences of DNA

• Any group of individuals have DNA sequences that are 99.9% identical regardless or origin or ethnicity.

• Points in DNA sequence where the sequences are not identical between two or more individuals are called single nucleotide polymorphisms (SNPs)

HPG has Raised Ethical, Social and Legal Issues

• Who owns genetic information?

• Should people be tested for genetic disorders if there is no possibility of treatment?

How Do We Use Biotechnology?

• Gene therapy: treatment of a genetic disease by alteration of the affected person’s genotype, or the genotype of the affected cells.

Stem Cells

• Definition: undifferentiated cells in either an adult or embryo that can undergo unlimited number of cell divisions.– Are totipotent

• Could be used to produce complex human tissues or replacement organs for people suffering from disease.

Designer Drugs

• Biotechnology has made it possible to predict the precise shape of molecules.– Makes it possible to develop drugs for

therapeutic use.

DNA in The Courtroom• Can be use to determine paternity• Identifying individuals in criminal and civil

proceedings.• Use variable number tandem repeats (VNTR) as

markers.

DNA in The Courtroom

Biotechnology on The Farm

• Goal: To increase the world’s food production while decreasing the costs and environmental damage due to insecticide and pesticide use.

Biotechnology on The Farm• Scientists have focused efforts on three areas:

– Developing crops capable of fending off insect pests without the use of insecticides

– Engineering plants with a greater yield that grow in a wider ranges of climates

– Make crops that are resistant to herbicides , so that fields can be treated for weeds without damaging crops

• Opponents wondering if we are disturbing ecological balance in the environment

Can Biotechnology Save The Environment?

• Bioremediation: Use of microorganisms to decompose toxic pollutants into less harmful compounds.

Risks of Biotechnology

• Two categories of risks:

– Risks to human health

– Risks to the environment

Questioning The Ethics of Biotechnology

• Privacy and ownership of genetic information.

• Argue altering genes is unnatural.– Breaches fundamental boundaries between

species.• Are scientists interfering with the order of

life?

Where Are We Now?