Stem Cells and Cellular Differentiation PDF

Stem Cells and Cellular Differentiat ion Multicellular Organisms Humans are made of millions of cells. This has a number of benefits: Cells can be specialized to do particular tasks Groups of cells can function as organs, making a more efficient but complex organism The o...

Stem Cells and Cellular Differentiat ion Multicellular Organisms Humans are made of millions of cells. This has a number of benefits: Cells can be specialized to do particular tasks Groups of cells can function as organs, making a more efficient but complex organism The organism can grow Quick Review Chromosomes: consist of wound-up DNA (genetic information in the form of genes). Genes: Segments of DNA that code for traits. There are MANY genes on each chromosome. Ex: You have a gene that codes for you hair color, a Humans have 23 pairs of chromosomes in every single body cell  If all your cells have the same Guiding DNA, how do they end up having Question different structures and Every Multicellular Organism Begins as a Single Stem Cell Every cell in your body has a complete set of chromosomes. Forensic scientists can take ANY cell they find at a crime scene (blood, skin, semen, hair…) and find a complete set of DNA within it. What’s so special about stem cells anyhow? They’re NOT SPECIAL(ized)  What is a specialized cell? Specialized Cells differ in structure carry out specific functions within the body. Nerve cells Skeletal muscle Epithelial cells (skin) Bone cells Red blood cells Intestinal Cells Cardiac muscle cells...to name a few. Cells must be shaped to perform specific functions in the context of the organism. If there was no cellular specialization, every cell in your body would be the same Cell Ex: Cells in your stomach are specialized to Specializ secrete mucus that protects your stomach wall from the extremely acidic stomach contents ation Ex: Nerve cells are responsible for the rapid conduction of messages throughout the body. Their FORM fits their FUNCTION Red Blood Cell Contain hemoglobin to carry oxygen to the cells. Thin outer membrane to let oxygen diffuse through easily. Shape increases the surface area to allow more oxygen to be absorbed efficiently. No nucleus, so the whole cell is full of hemoglobin. Their FORM fits their FUNCTION Nerve Cells (Neurons) Neurons are highly specialized to transmit messages from one part of your body to another. All neurons have a cell body and one or more fibers. These fibers vary in length from microscopic to over 1 meter. Some fibers carry information towards the cell body, called dendrites, and some fibers that carry information away from it, called axons. Stem Cells Unlike specialized cells, which have a specific form and function, stem cells are not specialized. Meaning, they have the POTENTIAL to become any kind of cell. Stem cells are found in a few places: Embryos (when they are about 4-5 days old) Few reserves in adults.  How do we get from stem cells to specialized cells? Cell Differentiation: the specialization of cells occurring during an organism’s development Cell Differentiation This 4-5 day old fetus (blastocyst) contain STEM CELLS that have the potential to become any kind of cell. Specialized cells can only make more specialized cells. Ex: Heart cells can ONLY make more heart cells. Blood cells can ONLY make more blood cells, etc Think, Pair, Share: Based on this information, and diagram, what do you think the words Pluripotent and Unipotent mean? How’d you do? Pluripotent: (many potentials) capable of giving rise to several different cell types. Unipotent: (one potential) capable of giving rise to only one cell type. Gene The turning on and off of genes within a cell in response to environmental stimuli or other factors (like Regulati developmental stage). A gene that is turned “on” means on it is being transcribed and translated into a protein. Of the millions of genes in each strand of DNA, only a small percentage are actually EXPRESSED (translated to protein) in a specialized cell. In skin cells, the only genes that are Gene translated to protein are the ones that code for skin cell properties! Express ion In white blood cells, the only genes that are translated to protein are the ones that code for white blood cell properties! Let’s say this represents all the DNA in a cell. SKINCELLHEARTCELLMUSCLECELLSMALLINTESTINECELLHAIRCELLVEINCE LL Each cell in your body has the complete instructions to make an entire person (you). However not all of your DNA is active in each cell.  Gene Regulation & Expression SKINCELLHEARTCELLMUSCLECELLSMALLINTESTINECELLHAIRCELLVE NC Gene Regulation: what part of the DNA is activated Gene Expression: What type of protein is created  Gene Regulation & Expression SKINCELLHEARTCELLMUSCLECELLSMALLINTESTINECELLHAIRCELLVE NC Gene Regulation: what part of the DNA is activated Gene Expression: What type of protein is created All cells contain a complete set of DNA Specialized cells only have certain genes that are expressed. Specialized cells are unipotent: can only make more specialized cells KEY Stem cells have NO gene regulation, and are therefore UNSPECIALIZED POINTS Stem cells are pluripotent: can give rise to ANY type of cell The differences between cell types is due to selective genes being expressed.