1. Unit 3 Biology: signatures of life conceptual 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
Much of Unit 3&4 biology explores the dynamic nature of the cell

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

3. Molecular 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

4. Inherited 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)

5. Inherited diseases Knowledge 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)

6. Gene 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

7. Gene therapy

8. Viral 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

9. Retroviruses
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)

11. Adenoviruses
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

12. Adenoviruses

13. Viral 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

14. Non 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

15. Medical diagnosis: Pre-Natal Testing
Used to determine if baby has a genetic defect
Done via:
Ultrasound: physical defects
Biochemical test on embryonic cells or amniotic fluid: metabolic defect

16. Medical 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 weeks
Collecting a sample of amniotic fluid surrounding the fetus

18. Medical diagnosis

19. Medical diagnosis: Presymptomatic 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

20. Rational 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

22. Rational 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

23. Rational 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

24. Manufacturing biological molecules
Genetically engineering proteins that are deficient (eg insulin)

25. Nanoparticles 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

26. Activity/homework Complete the Molecular Biology exam questions
Chapter 4 Quick Check qu 1-16

27. Reflection
What did you learn about molecular biology today?