Unit 3 Biology: signatures of Unit 3 Biology: signatures of lifelife

conceptual frameworkconceptual framework

Chemical nature of the cell

The nature of molecules

Interactions between molecules determine shape of biomacromolecules and produces binding sites for:•enzymes and substrates•Signals and receptors•Antibodies and antigens

Explains how:•various materials enter and leave a cell•Cells receive and respond to signals•How the immune system works•How vaccines work•How we design drugs

Molecular biology in Molecular biology in medicinemedicine

EL: To explore the application of molecular biology in medicine.

Molecular biologyMolecular biology

Applications of molecular biology in medicine, include:

Knowledge and manipulation of genetic material

the development of designer drugs to:◦ Prevent action of infective micro-organisms◦ Inhibit the action of specific chemicals in

the body

the production of hormones and plant vaccines

Inherited diseasesInherited diseases

Also known as genetic disorders

Exist because of defect in kind or amount of DNA in the affected organism

Many different types◦Eg a whole chromosome may be

involved or just a single gene (NB. We’ll only focus on single gene defects)

Inherited diseasesInherited diseasesKnowledge about the gene

responsible may allow:

◦Testing for the presence of the defective gene (eg breast cancer gene, phenylketonuria (PKU)

◦Special treatment to delay onset of the disease

◦Reducing severity of condition through treatment (eg cystic fibrosis) or special diet (eg galactosaemia, PKU)

Gene therapyGene therapy

The insertion of a normal functional gene into cells that contain a defect

Two types:◦ in vivo: gene therapy given directly to

patient◦ex vivo: gene therapy in which the

patient’s cells are manipulated outside the body and then returned into the individual

The specially prepared functional piece of DNA inserted into the cell is called a cloned gene

Gene therapyGene therapy

Viral Gene therapyViral Gene therapy

A vector is used to carry the gene into a cell

Most commonly used vectors are viruses ◦ Viruses with DNA replicate in the nucleus of

the cells they infect◦ Viruses with RNA replicate in the cytoplasm

of the cells they infect Exception is RNA viruses called retroviruses – they

also replicate in the nucleus

Most commonly used vectors in gene therepy are retroviruses and adenoviruses

RetrovirusesRetroviruses

Only used in cells that are reproducing when nuclear membrane breaks down and chromosomes of infected cell become accessible

Useful for cells that can be taken out an cultured outside the body (eg blood, bone marrow)

AdenovirusesAdenoviruses

DNA viruses – enters nucleus but remains separate from the host DNA

The cloned DNA is functional and produces functional protein

May be short-lived as this small piece of DNA doesn’t replicate when the host cell does

AdenovirusesAdenoviruses

Viral Gene therapyViral Gene therapy

Still experimental in humans and can pose risks to patients safety, eg◦Temporary solution◦Insertion into wrong place on

chromosome, causing a different disease

◦Immune response to virus

Non viral Gene therapyNon viral Gene therapy

As yet, not very successful

Methods include◦Transporting DNA into cells in lipid

spheres◦Direct injection of DNA into cells◦Manufacture of artificial

chromosomes

Medical diagnosis: Pre-Natal Medical diagnosis: Pre-Natal TestingTesting

Used to determine if baby has a genetic defect

Done via:◦Ultrasound: physical defects◦Biochemical test on embryonic cells

or amniotic fluid: metabolic defect

Medical diagnosisMedical diagnosis

Obtaining a sample of embryo cells can be done through:◦Chorionic villus sampling:

at 6-8 weeks Removal of a small piece of chorion

tissue

◦Amniocentesis At 16-18 weeks Collecting a sample of amniotic fluid

surrounding the fetus

Medical diagnosisMedical diagnosis

Medical diagnosis: Medical diagnosis: Presymptomatic testingPresymptomatic testing

Breast cancer: women with BRCA1 or BRCA2 gene have 80% risk of developing breast cancer (compared with 10% in rest of population)

Tests exist for the gene an women who test positive may either:◦have their breasts removed before

they develop the disease, or◦get regular mamograms

Rational drug designRational drug design

When a drug is designed to act against an infective agent:

◦The molecular structure of the active site of the infective agent is established

◦The drug is designed to have a complementary structure

◦The drug locks into the active site to prevent development of the disease

Rational drug designRational drug design

When a drug is designed to inhibit the action of a chemical in the blood:◦The molecular structure of

chemical is established◦The drug is designed to have a

structure that locks into the active site of the chemical

◦The chemical is inactivated

Rational drug designRational drug design

The delivery of vaccines in plant material as food involves:◦Determining the molecular structure of

the proteins in the infective agent that cause the immune response

◦Introducing the DNA that codes for these proteins into the plant genome

◦Growing and harvesting the plants

eg measles vaccine in powdered lettuce, cholera vaccine in rice

Manufacturing biological Manufacturing biological moleculesmolecules

Genetically engineering proteins that are deficient (eg insulin)

NanoparticlesNanoparticles

Nanoparticles are:◦Manufactured◦1-100 nanometers (one billionth of a

meter) in diameter◦Made of a double layer of phospholipids

to mimic plasma membrane of the cell

Used to deliver toxic drugs directly to target cells (eg tumour cells), reducing the chance of affecting healthy cells

Activity/homeworkActivity/homeworkComplete the Molecular Biology

exam questions

Chapter 4 Quick Check qu 1-16

Reflection Reflection What did you learn about

molecular biology today?