Ch 12. Mitosis

Ch 12. Mitosis - Chromosomes the Cell Cycle Cell Division...

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Chapter 12 Cell Division In bacteria and unicellular eukaryotes: cell division is used only as a means to reproduce asexually o Bacteria usually divide by binary fission (asexual division) o Eukaryotes divide by mitosis (nuclear division) followed by cytokinesis (cytoplasmic division) In multicellular eukaryotes, cell division (mitosis) can also be involved in growth & development as well as tissue repair . Replicating the instruction booklet When cells divide, each resulting “daughter” cell must receive a complete set of DNA instructions in order to survive. Organization of DNA o DNA is complexed with proteins to form chromatin , which is folded and coiled to form dense chromosomes. o The packaging of long strands of DNA into chromosomes facilitates their sorting and division. Eukaryotic Chromosome Structure: Somatic cells are Diploid = two complete sets of genetic information o For instance, humans have 23 pairs of chromosomes, or 46 total o that is, there are 2 copies of each chromosome, one from the individual’s mother (via the egg), and one from his/her father (via his sperm) alleles-different forms of genes. .diff info but apply to a certain trait In contrast, germ cells (eggs, sperm) are haploid o contain only one set of chromosomes (23 in humans), formed by meiosis (Ch 13) Eukaryotic Chromosomes cont. DNA must be duplicated before a cell can form daughter cells Duplication occurs during the S (synthesis) stage of a cell’s cycle After being duplicated, each Chromosome consists of 2 chromatids (copies) joined by a centromere o individual chromosomes can be recognized by their length, the position of their centromere and their banding pattern Cell Cycle = The rhythm of cellular life. Cells must do more than divide. o They must metabolize energy and products to stay alive. o They must do their job in a multicellular organism. The cell cycle of somatic cells includes: Mitosis plus Interphase (G1 + S + G2) o Most of a cell’s life is spent in interphase Cell Cycle = The rhythm of cellular life. Some cells divide only one time
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Ch 12. Mitosis - Chromosomes the Cell Cycle Cell Division...

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