RVHS 13. Stem Cells 9477

River Valley High School 1 2025 JC1 H2 Biology Lecture Topic 13: Stem Cells River Valley High School 2025 JC1 H2 Biology Lecture Topic 13: Stem Cells Name: ( ) Class: 25J__ Date: References Title Authors Biology (9th Edition) Campbell and Reece Introduction to Biotechnology (2nd Edition) Thieman and Palladino Stem Cells for Dummies (2nd Edition) Goldstein and Schneider H2 Biology Syllabus 9477 (2025) Candidates should be able to use the knowledge gained in the following section(s) in new situations or to solve related problems. Related Topic Concepts Organelles and Cellular Structures Cell Theory Learning Outcomes 1D. Stem Cells a. 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) b. Explain the normal functions of stem cells in a living organism, including embryonic stem cells and blood stem cells (lymphoid and myeloid). Lecture Outline I. Nature of Stem Cell A. Terminology B. Origin of Stem Cells II. Types of Stem Cell A. Zygotic Stem Cells B. Embryonic Stem Cells C. Adult Stem Cells III. Applications of Stem Cell A. Stem Cell Research B. Ethical Implications C. Human Induced Pluripotent Stem Cells

River Valley High School 2 2025 JC1 H2 Biology Lecture Topic 13: Stem Cells Websites URL Description https://www.dnalc.org/resources/animations/stemcells.html Numerous animations on stem cells https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7367472/ Review paper on stem cell-based therapies I. NATURE OF STEM CELL A. Terminology Differentiation ⬧ The gradual appearance of characteristic cellular specialisations during development as the result of gene activation or repression. Stem cell ⬧ A relatively unspecialised cell that can o divide and grow indefinitely o differentiate into specialised cells of one or more types under appropriate conditions ⬧ Hence, stem cells are able to replenish their own population and to generate cells that travel down specific differentiation pathways. ⬧ In some cases, stem cells also may undergo asymmetric division, in which one daughter cell retains its stem cell properties and the other undergoes differentiation and develop into a specialised cell. Totipotency ⬧ Describes a cell that can give rise to all parts of the embryo and adult, as well as extra -embryonic tissues in species that have them. ⬧ Totipotent cells can differentiate into any cell type to form whole organisms. ⬧ In mammals, only zygote and the first four cells derived from a zygote are totipotent. They give rise to all the cells in the adult as well as the cells that form the placenta and umbilical cord, without which no foetus can survive Pluripotency ⬧ Describes a cell that can give rise to many, but not all parts of an organism ⬧ Pluripotent cells can differentiate into almost any cell type to form any organ in the organism. ⬧ In mammals, embryonic stem cells are pluripotent. They can give rise to any cell type except those that form the placenta and the umbilical needed to establish and maintain a pregnancy Multipotency ⬧ Describes a cell that can give rise to some parts of an organism ⬧ Multipotent cells can differentiate into a limited range of cell types in a specific category of cell. ⬧ In mammals, adult stem cells (e.g. lymphoid and myeloid stem cells) are multipotent. They can give rise to lots of different cell types, but usually not all the cell types in an adult body.

River Valley High School 3 2025 JC1 H2 Biology Lecture Topic 13: Stem Cells B. Origin of Stem Cells ⬧ In mere 40 weeks, what begins as a single cell (zygote) becomes an individual whose body contains trillions of cells organised into a complex array of highly specialised structures. ⬧ All the tissues, organs and organs systems take shape and begin to function. ⬧ The creation of different types of cells required by this process is called differentiation, which occurs through selective changes in genetic activity, during which some genes are turned on and others are turned off. ⬧ Stages of development from fertilisation to maturity: o development begins at fertilisation / conception. o embryological development comprises events that occur during the first two months after fertilisation o foetal development begins at the start of the ninth week and continues till birth

River Valley High School 4 2025 JC1 H2 Biology Lecture Topic 13: Stem Cells Fertilisation to Embryological Development ⬧ At the moment of fertilisation, the fertilised ovum is a single cell (zygote) that has a diameter of about 0.135mm and a weight of approximately 150mg. ⬧ By the end of the first trimester (12 th developmental week), the foetus is almost 75 mm long and weighs approximately 14g. ⬧ Many important and complex developmental events occur during the first trimester. The four general processing include: 1. Cleavage A sequence of mitotic cell divisions that begin immediat ely after fertilisation, ending at the first contact with the uterine wall. During cleavage, the zygote develops into a multicellular complex known as a blastocyst. 2. Implantation Implantation begins with the attachment of the blastocyst to the uterine wall and continues as the blastocyst invades maternal tissues. 3. Placentation Placentation occurs as blood vessels form around the periphery of the blastocyst and the placenta develops. The placenta is a complex organ that permits exchange between the maternal and embryonic circulatory systems. 4. Embryogenesis Formation of a viable embryo.

River Valley High School 5 2025 JC1 H2 Biology Lecture Topic 13: Stem Cells II. TYPES OF STEM CELL A. Zygotic Stem Cells ⬧ A totipotent zygote cell is formed by the fusion of ovum and sperm. ⬧ A series of mitotic cell divisions that subdivide the cytoplasm of the totipotent zygote. ⬧ The first cleavage produces a pre-embryo consisting of two identical cells. ⬧ The first four cells derived from a zygote are totipotent. Totipotent cells give rise to all the cells in the adult as well as the cells that form the placenta and umbilical cord, without which no foetus can survive ⬧ Subsequent cell divisions produce identical cells called blastomeres. ⬧ During the initial divisions, all the blastomeres undergo mitosis simultaneously. As the number of blastomeres increases, the timing becomes less predictable. ⬧ After three days of cleavage, the pre-embryo is a solid ball of cells known as a morula. The morula typically reaches the uterus on day 4. ⬧ Blastocyst formation Over the next two days, the blastomeres form a blastocyst, a hollow ball with an inner cavity known as the blastocoel. ⬧ The blastomeres are no longer identical in shape and size. ⬧ The outer layer of cells, called the trophoblast, provides nutrients to the developing embryo. ⬧ The second group of cells, called the inner cell mass (ICM), lies clustered at one end of the blastocyst. The ICM will form the embryo.

River Valley High School 6 2025 JC1 H2 Biology Lecture Topic 13: Stem Cells B. Embryonic Stem Cells ⬧ The group of cells inside the blastocyst inner cell mass, consists of embryonic stem cells ⬧ These cells cannot be used to form whole cloned embryos as they cannot form a placenta if placed in a surrogate mother. ⬧ However, they do still have the ability to divide repeatedly and to develop into any other kinds of tissue. This group of cells is described as pluripotent. ⬧ The inner cell mass gives rise to the cells of the resulting three germ layers: endoderm, mesoderm, and ectoderm which eventually form all the highly speciali sed cells needed to produce an adult organism.