YIJC [H2] CI1.5_Stem Cells (N)

2024 JC1 BIOLOGY LECTURE NOTES CORE IDEA 1: THE CELL AND BIOMOLECULES OF LIFE TOPIC 1.5: STEM CELLS Learning Outcomes: (t) describe the unique features of stem cells, including zygotic stem cells, embryonic stem cells and blood stem cells (lymphoid and myeloid), correctly using the terms: i. totipotency (e.g. zygotic stem cells) ii. pluripotency (e.g. embryonic stem cells) iii. multipotency (e.g. lymphoid and myeloid stem cells) (u) Explain the normal functions of stem cells in a living organism, including embryonic stem cells and blood stem cells (lymphoid and myeloid) (v) Discuss the ethical implications of the application of stem cells in research and medical applications and how human induced pluripotent stem cells (iPSCs) overcome some of these issues. (Procedural details of how iPSCs are formed are not required). Use the knowledge gained in this section in new situations or to solve related problems. References: Reece, J. B. et al. (2018). Campbell Biology (11th Ed). Chapter 19: DNA Technology, pp. 460 – 465. Note: This textbook is available in our library. You may wish to borrow the book to supplement your reading when necessary. H2

2 1. What are Stem Cells? 1.1 Definition The stem cell is an undifferentiated and unspecialised cell that can divide over long periods and can produce specialised cell types in the body. 1.2 Properties All stem cells are different from other cells in the body in three main ways: 1. Stem cells are undifferentiated and unspecialised. • They do not have any tissue -specific structures that allow them to perform specific functions. o E.g. stem cells do not produce haemoglobin to carry oxygen through the bloodstream like a red blood cell • However, unspecialised stem cells can differentiate to become specialized cells, e.g. red blood cells. 2. Stem cells are capable of long-term self-renewal. • Stem cells can divide and produce copies of themselves (i.e. proliferation), to replenish their cell count. • Stem cells undergo mitotic division to produce two genetically identical daughter cells via: o symmetrical division which form 2 daughter stem cells o asymmetrical division where one daughter cell remains a stem cell while the other daughter cell becomes a progenitor cell which undergoes further division and differentiate into other specialised cell types. o A progenitor cell is a n immediate descendent of a stem cell that is fate-restricted. E.g. progenitor daughter cells of haematopoietic stem cells can only differentiate into various blood cell types (e.g. red blood cells, mast cells, neutrophils) and not other cell types. Fig. 1.1 Types of cell division in stem cells

3 Fig. 1.2 Division and differentiation of progenitor cell 3. Stem cells can differentiate. • Stem cells have the potential to become other more specific cell types. These new cells used to replace damaged or diseased cells of the tissues a