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Published byThomasina Johnson Modified over 8 years ago
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Cell Reproduction Mitosis
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Chromosomes Made of DNA Wrap around histone proteins to become chromatin
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Chromosomes Chromatin wind up further to become chromosomes Each half of a chromosome is a chromatid Chromatids are held together in the center at the centromere
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Chromosomes Sex chromosomes determine an organism’s sex Females = XX Males = XY Number of sex chromosomes in a human cell is 2
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Chromosomes Autosomes – all the chromosomes except for the sex chromosomes Number of autosomes in humans = 44
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Chromosomes Homologous chromosomes – every cell in sexual organisms has two copies of each autosome
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Chromosomes Humans have 44 autosomes so they have 22 homologous pairs. Dogs have 76 autosomes so they have 38 homologous pairs. –Goat = 58 –Armidillo = 62 –Chicken = 78 –House fly = 12 –Mosquito = 6
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Diploid Cells with 2 sets of chromosomes (homologous prs.) are diploid. In humans, the diploid number is 46 (2n)
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Haploid Cells with one set of chromosomes are haploid. In humans, the haploid number is 23 (1n).
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Cell Division -Prokaryotes Bacteria do not have a nucleus. They divided by a process known as binary fission.
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Binary Fission Chromosomes replicate The cell grows to twice its original size The cell divides into two identical cells
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Cell Division in Eukaryotes Eukaryotes have a nucleus in their cells Mitosis: results in new cells with identical genetic material Meiosis: results in new cells with half the number of chromosomes
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Cell Cycle Set of events that make up the life of a cell
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Interphase Takes up most of the cell’s lifespan (up to 90%)
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Interphase G1 phase – cell grows to mature size S phase – DNA replication G2 phase – cell prepares for division
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Mitotic Phase Series of events that allows a cell to divide Prophase Metaphase Anaphase Telophase
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Prophase DNA winds up into chromosomes Centrioles appear at opposite ends of the nucleus
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Prophase Spindle fibers form Chromosomes attach to spindle fibers Nuclear membrane and nucleolus disappear
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Metaphase Chromosomes move to the center (equator) of the cell
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Anaphase Chromatids separate by the centromere They are now considered to be individual chromosomes
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Telophase Spindle fibers disappear Chromosomes begin to unwind into chromatin Nuclear membranes begin to form
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Cytokinesis Immediately follows mitotic division The cell membrane is split in half
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Animal Cytokinesis The membrane pinches off into two new cells
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Plant Cytokinesis A cell plate forms in the center. The plate separates the two cells.
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