2. Higher Human Biology Unit 1 – Key area 1

3. Differentiation and Stem Cells

4. Learning Outcomes o Differentiation: During embryological development the unspecialised cells of the early embryo differentiate into cells with specialised functions. o Stem cells: Stem cells are relatively unspecialised cells that can continue to divide and can differentiate into specialised cells of one or more types. o In the very early embryo, embryonic stem cells differentiate into all the cell types that make up the organism. o Tissue (adult) stem cells replenish differentiated cells that need to be replaced and give rise to a more limited range of cell types. o Tissue (adult) stem cells in the red bone marrow give rise to red blood cells, platelets and the various forms of phagocytes and lymphocytes. o Once a cell becomes differentiated it only expresses the genes that produce the proteins characteristic for that type of cell.

5. Introduction The human body is made up of many specialised cells that perform specific functions. Specialised cells arise from the differentiation of unspecialised cells during embryological development. Differentiation is when an unspecialised cell becomes specialised in structure and biochemical properties, making them perfectly adapted for carrying out a particular function. Stem cell animation

6. Examples of Differentiation

7. Ciliated epithelial cells line the trachea (windpipe) It has an axon (a long, insulated cytoplasmic extension). This structure is perfectly suited for transmitting nerve impulses. This is because those cells are only expressing the genes for neurotransmitters. motor neuron cell They are perfectly suited to their job of sweeping dirty mucus up and away from the lungs. This is because those cells are only expressing the gene that codes for mucus. This means that the mucus gene is switched on and other genes, like the one that codes for insulin, are switched off.

8. Stem cells…what do you know already? Use the questions below to help you complete a KWL chart to show the following information: K what you know already W what you want to learn about stem cells during this unit L complete this at the end of the unit to summarise what you have learned Some questions to think about… What is a cell? What varieties of cell exist? What is a tissue? Give some examples. What is an organ? Give some examples. What is a system? Give some examples. What is a stem cell? What are some different types of stem cells? What is the purpose of stem cell research? What are some ways that stem cells have been successfully used in medicine? What are some of the issues in stem cell research? What are some of the misconceptions that people have about stem cell research?

9. What are stem cells? Stem cells are unspecialised cells that have the ability to reproduce and differentiate into a diverse range of specialised cells.

10. Types of stem cells Embryonic Adult

11. Embryonic stem cells Embryonic stem cells are derived from an embryo about 4–5 days old (blastocyst). These cells have the ability to differentiate into all of the cell types that make up an organism.

12. Adult (tissue) stem cells Adult or tissue stem cells are found in small numbers in the tissues and organs of adults and children, including the brain, bone marrow, skeletal muscle and skin. These cells give rise to a much more limited range of cell types and will tend to develop into cell types that are closely related to the tissue in which they are found. These cells replenish differentiated cells that need replaced in the tissues in which they are found.

13. Example of Adult Stem Cells

14. Other types of stem cells Stem cells can also be taken from the umbilical cord of new babies. Like adult stem cells, these cells can differentiate into a limited range of specialised cells.

15. Induced pluripotent stem cells Induced pluripotent stem cells are adult cells that have been genetically reprogrammed to an embryonic stem cell-like state. http://www.bbc.co.uk/news/science-environment-19878542 http://www.bbc.co.uk/news/science-environment-19872346

16. Questions 1.Define the term differentiation. 2.In what way is a ciliated epithelial cell a good example of a specialised cell? 3.A goblet cell in the lining of the trachea produces mucus but not insulin. Explain briefly how this specialisation is brought about with reference to genes. 4.Give two characteristics of stem cells. 5.Name two types of stem cells found in humans. 6.For each type of stem cell (Q5), identify one location where these cells can be found. 7.Which type of stem cell is capable of differentiating into all the types of cell that make up the organism to which it belongs?

17. Answers 1.Unspecialised cells of the early embryo become specialised in structure and biochemical properties, making them adapted for carrying out a particular function. 2.They are a good example as they are perfectly suited to their job of sweeping dirty mucus up and away from the lungs. 3.The cell is now only expressing the gene that codes for mucus/ only the mucus gene is switched on. The gene that codes for insulin is switched off. 4.Two characteristics of stem cells are 1.They reproduce themselves by repeated mitosis 2.They can differentiate into specialised cells. 5.Two types of stem cells in humans are 1.Embryonic 2.Adult 6.Embryonic stem cells are found in embryo blastocysts, Adult stem cells are found in bone marrow, skin, skeletal muscle, brain. 7.Embryonic

18. Differentiation in Somatic Cells

19. Learning Outcomes o Somatic cells form different types of body tissue. Epithelial cells cover the body surface and line body cavities, connective tissue includes blood, bone and cartilage cells, muscle cells form muscle tissue and nerve cells form nervous tissue. o The body organs are formed from a variety of these tissues. During cell division the nucleus of a somatic cell divides by mitosis to maintain the diploid chromosome number. Diploid cells have 23 pairs of homologous chromosomes.

20. Somatic cells Somatic cells are the differentiated cells that form the different types of body tissue that exist.

21. Somatic cells B Lymphocyte Hyaline cartilage Smooth muscle

22. Somatic cells Ciliated epithelial cell Red blood cell platelets neutrophil

23. Somatic cells Cardiac muscle Nerve cells Squamous epithelial cells T lymphocyte

24. Increasing Level Of Complexity Cells  Tissues  Organs  Systems  Organism

25. Questions 1.Name three different types of differentiated tissue derived from somatic cells in addition to connective tissue. 2.Arrange the following terms in order of increasing complexity: body, cell, organ, system, tissue. 3.Briefly describe how chromosome number is maintained in a somatic cell at cell division.

26. Answers 1.Epithelial, bone, cartilage, muscle (Any 3 of). 2.Cell  Tissue  Organ  System  Body 3.Before nuclear division, the genetic material in a cell undergoes replication and becomes doubled. This is followed by nuclear division and the genetic information is divided equally between the two daughter nuclei. Therefore each somatic cell formed receives an identical copy of the full set of 46 chromosomes (23pairs).

27. Differentiation in Germline Cells

28. Learning Outcomes o The nucleus of a germline cell can divide by mitosis to produce more germline cells or divide by meiosis to produce haploid gametes. o Mutations that occur in germline cells will be passed to offspring whereas mutations in somatic cells will not.

29. Germline cells Germline cells include the gametes and the cells that produce the gametes.

30. Division of germline cells Germline cells are diploid (23pairs of homologous chromosomes). Germline cells can divide by mitosis to produce more germline cells. Gamete mother cells divide by meiosis to produce gametes.

31. Mutations Mutations in germline cells are passed onto offspring. – For example: Cystic Fibrosis A gene mutation on chromosome 7 may become the recessive form (leading to production of thick and sticky mucus). This mutant allele is passed onto gametes during meiosis. If the other parent is a carrier of the same recessive allele then the resulting zygote will be a cystic fibrosis sufferer. A mutation in a somatic cell, even if it leads to a phenotypic change, is not passed onto offspring.

32. Questions 1.What is the difference between the terms haploid and diploid? 2.What is a germline cell? 3.Describe how a diploid germline cell produces haploid gametes. 4.In which type of cell (somatic or germline) is a mutation not passed on to the members of the next generation?

33. Answers 1.Haploid means a single set of 23 chromosomes. Diploid is a double set of chromosomes – 46 Chromosomes arranged as 23 pairs. 2.Germline cell is a cell that will eventually lead to the formation of sex cells (gametes). 3.By a form of nuclear division called Meiosis. The genetic material is doubled then it is divided between 4 nuclei. Each receives a set of 23 single chromosomes. 4.Mutations in Germline cells are passed onto members of the next generation.

34. Research and Therapeutic Value of Stem Cells

35. Learning Outcomes Stem cell research provides information on how cell processes such as cell growth, differentiation and gene regulation work. Stem cells can also be used as model cells to study how diseases develop or for drug testing. The therapeutic uses of stem cells include bone marrow transplants, skin grafts for burns and stem cell grafts for cornea repair. The ethical issues of stem cell use and the regulation of their use

36. Stem cell research Stem cell research provides us with a wealth of information and can be studied in a variety of ways, including: how cell processes such as growth, differentiation and gene regulation work the study of diseases and their development drug testing therapeutic uses in the treatment of diseases such as leukaemia (bone marrow transplant), Hunter’s disease and heart disease therapeutic uses in medicine, including skin grafts for burns and stem cell grafts for cornea repair.

37. For example, stem cells could be turned into new bone cells and then injected into weak or broken bones. Skin cells could replace burnt skin, and brain cells could help people who have suffered brain damage. Or they could become nerve cells that could heal spinal cord injuries. Stem cells could be taken from someone with heart disease and be turned into heart cells, which can gather in a dish and throb! They could then be injected back into the patient to rebuild their heart tissue and combat heart disease.

38. Parkinson's is a very common disease starting with mild symptoms, a mask-like face, stiffness and tremors until sufferers eventually become immobile. It is caused by a slow deterioration of certain brain cells (neurons) and there's no cure. Replacing the affected brain cells seems more hopeful than finding better drugs. Many people think that stem cells could be grown into new brain cells that could help to treat or even cure Parkinson's. Parkinson's disease

40. Windpipe Transplant http://www.bbc.co.uk/learningzone/clips/wo man-gets-windpipe-transplant/5857.html http://www.bbc.co.uk/learningzone/clips/wo man-gets-windpipe-transplant/5857.html

41. Therapeuti c stem cell cloning

42. Video Clips – Stem Cells and Ethics http://www.educationscotland.gov.uk/video/h/video_tcm4664297.asp?strR eferringChannel=highersciences&strReferringPageID=tcm:4-658424- 64&class=l3+d142456+d143862 http://www.educationscotland.gov.uk/video/h/video_tcm4664297.asp?strR eferringChannel=highersciences&strReferringPageID=tcm:4-658424- 64&class=l3+d142456+d143862 http://www.bbc.co.uk/learningzone/clips/stem-cell-research-and- medicine/6013.html http://www.bbc.co.uk/learningzone/clips/stem-cell-research-and- medicine/6013.html http://www.bbc.co.uk/learningzone/clips/ethics-of-using-foetal-stem-cells- for-stroke-treatment/5888.html http://www.bbc.co.uk/learningzone/clips/ethics-of-using-foetal-stem-cells- for-stroke-treatment/5888.html http://www.bbc.co.uk/learningzone/clips/alternative-to-embryo-stem-cells- developed-by-researchers/6581.html http://www.bbc.co.uk/learningzone/clips/alternative-to-embryo-stem-cells- developed-by-researchers/6581.html http://www.bbc.co.uk/programmes/p00k7j7w http://www.bbc.co.uk/learningzone/clips/stem-cell-research/14287.html

43. Presentation task Using what you have learned already and adding further research, create a presentation that covers the following aspects of stem cells: the biology of stem cells – what is a stem cell, types of stem cells the potential of stem cells – details of one or two research projects involving stem cells that you have found particularly interesting, details of potential therapies stem cell dilemmas – explore the moral and ethical issues surrounding stem cell research (personal points of view can be expressed if desired). You will be assessed using all three of the above criteria as well as on the overall quality of your presentation.

44. Not in our back yard! Should a business license be issued to ESC lifeworks Inc. by the city of Glasgow?

45. ESC lifeworks Inc is a private corporation that has applied for a business license and has been offered premises within the city of Glasgow. The company wishes to construct a biotechnology research and development laboratory to develop stem cell therapies to treat Parkinson’s disease and other neurodegenerative diseases. A council meeting has been called to discuss whether or not a business licence will be issued. Council members must vote on the issue after the discussion.

46. Questions 1.Name one medical condition that is routinely treated using tissue stem cells. 2.From where in the human body are these cells obtained? 3.Give an example of a medical condition that might be treated in the future using stem cells. 4.Why does stem cell research using human embryos raise ethical issues? 5.Why is it important that stem cell research is carefully regulated?

47. Answers 1.Bone marrow transplants or skin grafts. 2.From donor bone marrow or by taking a small sample of skin cells. 3.Diabetes, Alzheimer's, Parkinson’s, spinal cord injury, Stroke. 4.It raises ethical issues because human embryos have the potential to become human beings. 5.To ensure the quality of stem cells used and the safety of the procedures are of the highest order and that there is no abuse of the system.

48. Cancer

49. Learning Outcomes o Cancer cells divide excessively to produce a mass of abnormal cells (a tumour) that do not respond to regulatory signals and may fail to attach to each other. o If the cancer cells fail to attach to each other they can spread through the body to form secondary tumours.

50. Cancer cells Cancer cells have many characteristics that make them different from normal cells: Cancer cells continue to reproduce to produce a mass of abnormal cells (a benign tumour). They do not respond to normal regulatory signals that would instruct them to stop dividing when necessary. They lose the molecules on their surface that would normally hold them in place and can therefore be detached from their neighbours, causing the cells to spread (malignant tumour). Skin cancer cells (melanoma)

51. HPV Certain strains of the human papilloma virus (HPV) have been shown to cause cervical cancer. The routine immunisation programme in Scotland is for girls aged 12 and 13 (S2). There is also a one-off, three-year catch-up programme for older girls.

52. Your task Produce an information leaflet designed to answer the questions of a patient recently diagnosed with cancer. Points to consider: How are cancer cells different from other cells? What is a tumour? How will I know if my cancer has spread? What is the difference between a malignant tumour and a benign tumour? How will my cancer be treated?

53. Bang Goes the Theory http://www.bbc.co.uk/programmes/p01vh3b h http://www.bbc.co.uk/programmes/p01vh3b h

54. Questions 1.Identify two characteristics of cancer cells.

55. Answers 1.Their division is uncontrolled and they do not respond to the usual regulatory signals.