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Lecture 34

BIOL 3040 Lecture 34: Lecture 34

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BIOL 3040

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APRIL 21 LECTURE 34 Practice questions: - The ectoderm becomes what two types of cells? o Neural and skin cells - Notch/Delta signaling is used to determine which cells become neural and which become skin, with neurons being the “winning” cell type, in the competition of lateral inhibition. If the Delta ligand is not expressed, what do the cells become? o All become neurons (and skin cells are absent) o when delta binds to notch, it turns off the neural signals - If the Notch receptor has a mutation which prevents its cleavage, what do the cells become? o Same as above—All become neurons, since Notch cannot activate transcription of the inhibitors of neuron fate o Delta/notch when active turns off neural Stem Cells - Cell turnover o Tissues vary enormously in their rate and pattern of cell turnover o Amount of time it takes to replace those cells o Terminally differentiated ▪ When they become a specific cell, the no longer divide o Precursor cells ▪ Proliferate but don’t divide forever ▪ Come from a small number of stem cells • Can divide forever • Self-renew • Hard to differentiate between stem cells and precursor cells - Stem cells o Division ▪ Divides into 2 different things ▪ Another stem cell and a precursor cell o Example ▪ Intestine stem cells • In the crypt of the lining is the stem cells • Divide every 24 hours • Yellow cells are precursor cells that move upward and out of the crypt o As they move up, they differentiate o When they get to the top, it undergoes apoptosis ▪ Secretions • secrete factors kill bacteria o Exocytosing in the direction of the gut o Paneth cell • Secretes hormones to stop feeling hungry o Enteroendocrine cells • Import nutrients o Absorptive cells • Secrete mucus o Globlet cells APRIL 21 LECTURE 34 o Types of stem cells ▪ Totipotent • Can form anything ▪ Pluripotent • Can make lots of different cells but not everything o Another example ▪ Hematopoietic stem cells • Can divid
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