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Biology Week 5 Notes

by: Kemjika Echebelem

Biology Week 5 Notes BIOL 2107K

Kemjika Echebelem
GPA 3.82

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About this Document

These notes summarize Ch. 11-12
Principles of Biology I
Class Notes
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This 8 page Class Notes was uploaded by Kemjika Echebelem on Tuesday July 12, 2016. The Class Notes belongs to BIOL 2107K at Georgia State University taught by Sylvester in Spring 2016. Since its upload, it has received 11 views. For similar materials see Principles of Biology I in Biology at Georgia State University.


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Date Created: 07/12/16
CH 11: CELL DIVISION – Variations, Regulation, and Cancer Binary Fission (For prokaryotes, like bacteria & archaea, and for mitochondria & chloroplasts; Very efficient) Circular DNA is  DNA Replication  Both DNA  As replication  Cell division  starts, the cell  begins w/the  Cell finally  attached to  starts &  molecules are  elongates equally  synthesis of a  divides into 2  membrane by  continues around  attached to  around the  new membrane  daughter cells proteins circle membrane by  midpoint at the mipoint proteins  Regulation of Cell Cycle: Cyclin – Cyclin-dependent kinase (Cyclin – CDK) complexes 1. Cyclins bind to and activate CDK’s 2. The activated CDK phosphorylates target proteins involved in promoting cell division Prophase/Prometaphase (P): S­Phase has replicated each linear * Mitosis/Cytokinesis is for somatic cells, cells in the body other tchromosome; Chromosomes condense and become visible;  Centrosomes radiate microtubules and go to opposite poles;  cells) use meiosis (used by humans to reproduce) Nuclear envelope breaks down; Spindle fibers attach to each  chromosome’s centromere, associated with 2 kinetochores (e.g.  Remember:  In humans: 46 types of chromosomes; 92 chromatids) ­ Eukaryotes have multiple, linear chromosomes (mitosis) Metaphase (M): Chromosomes align in center of cell; One of  ­ Prokaryotes have 1 circular chromosome (binary fission) the most visually distinctive phases under microscope ­ Sexual Reproduction requires diploid genome ­ Chromatids have nothing to do with being haploid & diploid;  Anaphase (A): Spindle fibers pull apart sister chromatids to  they’re just temporary structures formed in mitosis opposite sides of cell; # of chromosomes has not changed ­ Mitosis produces 2 daughter cells; each is diploid, like parent Telophase/Cytokinesis (T): Nuclear envelope reforms &  chromosomes decondense; each daughter cell is diploid (2  copies of each chromosome) like parent; Cytokinesis – Animals  Spindle Assembly Checkpoint: Are all the chromosomes attached to the spindle fibers? (before anaphase) Prophase/Prometaphase: M – cyclin – CDK complex: prepares cell for mitosis Majority of cells stay in G 0 Phase, where they don’t DNA Replication Checkpoint: Is all  actively divide the DNA replicated? (At end of G ) 2 G 1S – cyclin – CDK complex: prepares cell for DNA replication DNA Damage Checkpoint: Is DNA damaged?  (Before entering S ­ phase) ­ Normally, p53 is exported from the  nucleus & degraded ­ When DNA is damaged, a certain CDK  is activated & phosphorylates p53   S – cyclin – CDK complex: Helps  ­ Phosphorylated p53 can’t leave nucleus; initiate DNA Synthesis so its levels rise, activating transcription of a gene that expresses a CDK  inhibitor protein ­ This inhibitor protein blocks the activity of G 1S complex, pausing the cell cycle Meiosis (I & II)  Has 2 Parts; Produces 4 daughter cells, each of which are haploid (contains half the # of chromosomes as parent)  Each daughter cell is genetically unique, because of “crossing over” (prophase I) & random alignment of bivalents (metaphase  I) Prophase I: Chromosomes become  visible; chromosomes condense &  synapsis occurs (gene­for­gene  Metaphase II: Recombinant  Anaphase II: The spindle fibers  pairing); Each pair of chromosomes  chromosomes align in the center of  separate the sister chromatids  forms a bivalent (4­chromatid  cell  (which is the same as in Anaphase  structure); chiasmata (crossing  of Mitosis) over) appears & nuclear envelope  begins to break down Metaphase I: Homologous pairs line  Prophase II: At this point, the 2  Telophase II: Nuclear envelope  up in center w/ bivalents oriented  cells from meiosis I are both ready  reforms and each daughter cell (4  randomly with respect to each  to divide into 2 cells; Nuclear  total) is haploid (one copy of each  other; Nuclear envelope has broken  envelope breaks down and  single chromosome) down  chromosomes condense  Cytoplasmic Division (Male & Females) - Males: Meiosis I produces equal splitting;  Anaphase I: Homologous  Telophase I: 2 daughter cells  chromosomes are separated, but not  produced; each daughter cell  Meiosis II produces sperm cells forever contains recombinant chromosome  - Females: Meiosis I produces unequal splitting sister chromatids; this is what  pairs; No DNA synthesis occurs  & 2 cells freeze; monthly, Meiosis II makes 4  makes this phase different from  after this stage before prophase II;  cells w/unequal splitting (including oocyte,  Anaphase (Mitosis) nuclear envelope reforms which becomes egg cell) Cancer  - In the Rous experiment, the virus causing the cancer contains an altered version of a gene normally found in the host animal cell that plays a role in embryonic development and is involved in the control of cell division. This experiment eventually led to discovery of…  Oncogenes: the gene that causes cancer  Proto-oncogene: normal genes important in cell division that have the potential to become cancerous if mutated (promote cell division)  Tumor Suppressor Genes: genes that encode proteins whose normal activities inhibit cell division  Cell division is regulated by the cooperative effort of proto-oncogenes and tumor suppressor genes o The two types of genes must be agreement for cell division to happen How Cancer Develops: st 1. 1 tumor suppressor gene isn’t activated – normal cells show signs of cancer by reddening 2. Oncogene is activated, allowing for the division of benign “slow-growing” cancerous cells; not a threat to the cell yet nd 3. 2 tumor suppressor gene isn’t activated – benign tumor grows into a malignant tumor, which endanger the surrounding tissue 4. After 3 tumor suppressor gene hasn’t been activated, the cancerous tumor breaks out of the tissue and forms a metastasis at others parts of the body


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