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Download Genetics: Mitosis/Meiosis
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Part 2 • Cell reproduction of somatic cells (all cells except sperm/egg) • This is how we grow, develop, and repair • Involves chromosomes: Complex structure of coiled DNA that carries all genetic information (genes) • Chromosome # • Each species has a characteristic # of chromosomes • Humans: 23 pairs (46 total) • Dogs: 39 pairs • Corn: 20 pairs • Diploid: Pairs of similar chromosomes (from parents) • Haploid: one of each type of chromosome • Gametes (egg 23 / sperm 23) Types: Autosomes: Do not determine sex (1-22) Sex Chromosomes: determine sex (X,Y 23) Male = XY Female = XX • • • • • • Interphase Prophase Metaphase Anaphase Telophase Cytokinesis • Longest phase of cell’s life cycle • Increase in mass • Increase # of organelles • Replication of chromosomes (DNA) • G1 Phase: Gap prior to DNA replication • S Phase: DNA replication • G2 Phase: After DNA replication • Chromosomes are copied (#doubles) • Chromosomes appear as threadlike coils (chromatin) at the start, but each chromosome and it’s copy (sister chromosome) change to sister chromatids. • Mitosis begins (cell begins to divide) • Centrioles (poles) appear and move to opposite ends of cell. • Spindle fibers form between the poles. • Nuclear membrane breaks apart. • Chromatids (pairs of chromosomes) attach to the spindle fibers. • They are aligned in middle of cell. • Chromatids separate and begin to move to opposite ends of the cell. • Two new nuclear membranes (nuclei) form. • Chromosomes appear as chromatin (threads). • Cell membrane begins to pinch together. • Cell membrane continues to move inward to create two daughter cells. • Each daughter cell has it’s own nucleus with identical chromosomes. • Modern Biology Books: Pg. 140 Review ? 1-8 (graded) • A type of cell division in which the chromosome # is reduced by half. • Production of gametes (sex cells) – these cells have half the # of chromosomes. • 2 Major sections of Meiosis: • Meiosis I – reductive division • Interkinesis – 2 cells form each with only one chromosome from the pair. • Meiosis II - Double stranded chromosomes become single stranded chromosomes. • Cytokinesis – 4 haploid cells are formed which will become sperm or eggs. • Fertilization: Fusion of gametes = reconstitutes the proper # of chromosomes. • Trait: Genetic characteristic of an organism. • Gene: DNA sequence that codes for a protein (may lead to a trait). • Allele: Different forms of a gene.