1. M.B.Ch.B, MSC, DCH (UK), MRCPCH
Molecular Biology
Lec.4
Dr. Mohammed Hussein
M.B.Ch.B, MSC, DCH (UK), MRCPCH

2. Clinical applications
Genetic strategies in therapeutics
Recombinant DNA Technology
Gene Therapy
Techniques of genetic analysis
Blotting Techniques
Polymerase Chain Reaction (PCR)

3. Recombinant DNA Technology

4. Recombinant DNA Technology
Recombinant DNA technology allows a DNA fragment from any source to be joined in vitro with a nucleic acid vector that can replicate autonomously in microorganisms.

10. Gene Therapy

11. Gene Therapy
Gene therapy now offers potential cures for individuals with inherited diseases.
The initial goal is to introduce a normal copy of the gene that is defective into the tissues that give rise to the pathology of the genetic disease.

12. Ex Vivo: Cells modified outside the body, then transplanted back in.
In Vivo: Gene changed in cells still in body.

14. Techniques of genetic analysis

15. Techniques of genetic analysis
Techniques of genetic analysis are assuming an increasingly larger role in medical diagnosis.
These techniques, which once were a specialized part of medical genetics, are now becoming essential tools for every physician to understand.

16. Blotting Technique

18. The polymerase chain reaction (PCR)
Is a technique in which a selected region of a chromosome can be amplified more than a million-fold within a few hours.
The technique allows extremely small samples of DNA to be used for further testing.
The PCR has many different applications.
1. Comparing DNA samples in forensic cases
2. Paternity testing
3. Direct mutation testing
4. Diagnosing bacterial and viral infections

20. Paternity testing using PCR

21. M.B.Ch.B, MSC, MRCPCH, DCH (UK)
Dr. Mohammed Hussein
M.B.Ch.B, MSC, MRCPCH, DCH (UK)

22. Introduction

23. Tumor can be benign, pre-malignant, or malignant, whereas cancer is by definition malignant.

24. Cancer is a group of diseases characterized by unregulated cell growth and the invasion and spread of cells from the site of origin, or primary site, to other sites in the body.

25. Oncogenes Tumor suppressor gene Apoptosis Cancer Biology
Onco = Greek word “ tumor”
Apoptosis = Greek word “ falling off”

26. Cancer Normal Cell Killed Cancer No Cancer Oncogene Apoptosis
Tumor suppressor
gene
Killed Cancer
No Cancer

28. Oncogene
An oncogene is a gene that has the potential to cause cancer

29. Proto-oncogene
Proto-oncogenes are the normal genes involved in the regulation of controlled cell growth. When the proto-oncogene is mutated or overregulated, it is called an oncogene and results in unregulated cell growth and transformation

31. Proto-oncogenes These genes encode proteins that function as
Growth factors
Growth factor receptors
Signal transducing proteins
Nuclear transcription factors

32. Growth Factors

33. Growth Factors
Aberrant production of these proteins can result in aberrant transition from G0 to G1, with subsequent uncontrolled growth.

34. Growth Factors
Fibroblast growth factors (FGFs) are a family of proteins that are normally expressed during the proliferation of cells required for normal wound healing, but overexpression can lead to tumor formation.
Platelet-derived growth factor (PDGF) is a polypeptide that is normally important for extracellular matrix production, but overexpression may result in proliferation as a result of autocrine stimulation.

35. Growth Factor Receptors

36. Cell Surface Receptors
Are receptors that are embedded in the membranes of cells.
They are specialized integral membrane proteins that allow communication between the cell and the extracellular space.
The extracellular molecules may be hormones, neurotransmitters, cytokines, growth factors, cell adhesion molecules, or nutrients; they react with the receptor to induce changes in the metabolism and activity of a cell.

37. Structure of the cell surface receptors
Extracellular Domain
Transmembrane Domain
Intracellular Domain

38. Intracellular domain
The intracellular (or cytoplasmic) domain of the receptor interacts with the interior of the cell or organelle, relaying the signal.
Often, this is tyrosine kinase activity.

39. Growth Factor Receptors
Epidermal growth factor receptors (EGFRs)
Rearranged during transfection (RET)

40. Growth Factor Receptors
Epidermal Growth Factor Receptors (EGFRs): There are at least three members of this family of tyrosine kinase receptors,
erb B-1
erb B-2
erb B-3
Which, when mutated, lead to aberrant signaling and growth in the absence of the epidermal growth factor [EGF].

41. Overexpression of the growth factor receptor erbB-1, also known as HER2/neu, is associated with the development of breast cancers.

42. Rearranged during transfection (RET)
This is tyrosine kinase receptor
Does not directly bind growth factors
It is important in the transduction of a signal upon binding of Glial cell line–Derived Neurotrophic Factor (GDNF)
With mutations resulting in autonomous growth-promoting signals in the absence of ligand binding.

43. Mutations in RET are commonly associated with multiple endocrine neoplasia (MEN) syndromes, including MEN I, and MEN II.

44. Signal Transduction

45. Signal Transduction
Is the process by which a chemical or physical signal is transmitted through a cell as a series of molecular events, most commonly protein phosphorylation, which ultimately result in a response.

46. The next level at which defects in cell growth and development can occur is at the level of downstream signal transduction proteins.
Two such examples are given:
The ras gene
Nonreceptor tyrosine kinase proteins

47. Ras gene
A guanine triphosphate (GTP)-binding protein anchored to the inner cell membrane
In the inactive state, Ras binds guanosine diphosphate (GDP).
In stimulation of the cell by growth factor–ligand interactions, Ras exchanges GTP for GDP, leading to activation of downstream signaling events

49. The ras gene is the most commonly mutated oncogene in cancer, with 10% to 20% of tumors harboring mutations in ras.
Mutations in ras are found in a large number of tumors of the colon, pancreas, and thyroid.