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What happens to cells when an egg meets a sperm, then turns into an embryo and finally a fetus………. Embryological Development During embryological development the unspecialised cells of the early embryo differentiate into cells with specialised functions. Learning Outcomes • Explain differentiation in human cells • Give the term for unspecialised of cells and the process of differentiation • Explain how proteins can be expressed differently What is a stem cell? Stem cells are relatively unspecialised cells that can continue to divide and can differentiate into specialised cells of one or more types. stem cell SELF-RENEWAL (copying) REPRODUCE DIFFERENTIATION (specializing) stem cell specialized cell e.g. muscle cell, nerve cell Differentiation In the very early embryo, embryonic stem cells differentiate into all the cell types that make up the organism. Tissue (adult) stem cells replenish differentiated cells that need to be replaced and give rise to a more limited range of cell types. Bone Marrow …. Blood Cells NK cell T cell B cell dendritic cell platelets bone marrow megakaryocyte erythrocytes macrophage neutrophil eosinophil basophil specialized cells committed progenitors Tissue (adult) stem cells in the red bone marrow give rise to red blood cells, platelets and the various forms of phagocytes and lymphocytes. Gene Expression …. Once a cell becomes differentiated it only expresses the genes that produce the proteins characteristic for that type of cell. Pancreas cell Eye lens cell (embryo) Key: Active gene Nerve cell Crystallin Glycolysis enzyme genes gene Insulin gene Hemoglobin gene Inactive gene Compare and Contrast ..... Embryonic Stem Adult Stem Cells Cells Found / Location Gene Expression Differentiation into cells Somatic Cells 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. Somatic Cells 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. Modelling Mitosis! Delightful Donuts ..... Put these pictures in order ... Review 1. Name 3 different types of differentiated tissue derived from somatic cells in addition to connective tissue 2. What is the difference between haploid and diploid? 3. What is a germline cell? 4. Briefly describe how a diploid germline cell produces haploid gametes 5. Which type of cell (somatic or germline) is a mutation not passed on to the members of the next generation?