CELL DIFFERENTIATION

ENGAGE

EXPLORE CELL DIFFERENTIATION GAME

Stem Cells 4

A life story… Human development starts with just 1 cell – the fertilized egg. This cell divides to produce 2 ‘daughter cells’. These daughters divide, and their daughters divide again, and so on. There are a great many steps needed to form an adult body, or even a baby. Along the way, lots of different types of cells must be made.

What is a stem cell? stem cell stem cell SELF-RENEWAL (copying) specialized cell e.g. muscle cell, nerve cell DIFFERENTIATION (specializing)

Self Renewal or Differentiation Self renewal is needed to maintain a pool of stem cells to use throughout your life as to not run out. Differentiation is important because specialized cells are used up, damaged or die all the time during your life. Specialized cells cannot divide and make copies of themselves, but they need to be replaced for your body to carry on working. Example: billions of new blood cells every day Differentiation also makes all the different kinds of cell in the body during development of an embryo from a single fertilized egg.

Where are stem cells found? embryonic stem cells blastocyst - a very early embryo that has about 50 to 100 cells not yet implanted in the womb. tissue stem cells (adult stem cells) fetus, baby and throughout life 8

Embryonic Stem Cells: Where do we find them? blastocyst outer layer of cells = ‘trophectoderm’ cells inside = ‘inner cell mass’ culture in the lab to grow more cells fluid with nutrients embryonic stem cells taken from the inner cell mass Embryonic stem cells can make all the different types of cell in the body – scientists say these cells are pluripotent. 10

EMBRYONIC STEM CELLS Challenges: Scientists around the world are trying to understand how and why embryonic stem cells produce skin, blood, nerve or any other particular kind of specialized cell. What controls the process so that the stem cells make the right amount of each cell type, at the right time? The big challenge for scientists is to learn how to control these cells. If we could force embryonic stem cells to make whatever kind of cell we want, then we would have a powerful tool for developing treatments for disease. Example:new insulin-producing cells for patients with diabetes.

Tissue stem cells: Where we find them surface of the eye brain skin breast intestines (gut) testicles bone marrow muscles We all have stem cells in our bodies all the time. They replace cells that are damaged or used up. 12

Tissue stem cells: What they can do MULTIPOTENT blood stem cell differentiation found in bone marrow only specialized types of blood cell: red blood cells, white blood cells, platelets MULTIPOTENT Can make multiple types of specialized cells, but not all types 13

Induced pluripotent stem cells (iPS cells) cell from the body ‘genetic reprogramming’ = add certain genes to the cell induced pluripotent stem (iPS) cell behaves like an embryonic stem cell all possible types of specialized cells culture iPS cells in the lab differentiation Advantage: no need for embryos!

ELABORATE STEM CELLS POINTS OF VIEW

EVALUATE Which cell is undifferentiated? Nerve Cell Stem Cell Muscle Cell Sperm Cell

EVALUATE Which of the following most accurately describes the difference between stem cells and specialized cells? Specialized cells can divide repeatedly, and stem cells cannot. Specialized cells have a specific function, and stem cells do not. Specialized cells are found in embryos, and stem cells are not. Specialized cells can develop into any type of cell in the body, and stem cells cannot.

EVALUATE Which source of stem cells is the cause of ethical debate? Adult (Tissue) Stem Cells Embryonic Stem Cells Amniotic Stem Cells Induced Pluripotent Stem Cells

EVALUATE What is one reason some scientists favor the idea of stem cell research? Some consider an unborn embryo as living. Stem cells might be used to regrow vital human tissue. Human stem cells can only come from human embryos. Other countries have already begun to research applications of human stem cells.

EVALUATE EDPUZZLE - CELL SPECIALIZATION