BIO final exam - BIO final exam Replication -occurs in the...

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N# DNA N# DNA N# DNA ½ n DNA ½ n DNA BIO final exam Replication -occurs in the nucleus -occurs during the S phase of cell division, at the end of S phase all the dna is replicated, each copy remains attached to the original until cell division -molecules required for DNA replication: Nucleoside tri-phosphates: A,T,G,C A single strand of DNA (a template) Enzymes: DNA polymerase, gyrase, helicase -DNA replication begins at origins of replication - gyrase uncoils DNA - helicase breaks Hydrogen bonds - works in both directions at once (bi-directional) -DNA polymerase synthesizes a new strand of DNA - adds nucleotides to the growing chain - proofreads and edits -mutations = permanent changes to DNA sequence Can occur in replication External sources: Ultraviolet radiation x-rays alcohol Cell Division 2 kinds of cell division: Mitosis “asexual” Meiosis -Mitosis: Have 2 times the DNA at one point -Meiosis
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Allows sexual reproduction -chromosomes Can only be seen during cell division Made of DNA and protein Before cell division DNA condenses, then chromosomes are visible One molecule of DNA is a chromosome Organization into clumps called nucleosomes o Composed of 150 bases wrapped around 8 histones o Anything that evolved has some histone proteins DNA Replication - 2 molecules are copies of each other held together with proteins - Centromere holds them together - After DNA replication the number of chromosomes is doubles - After replication the DNA is in sister chromatid form - The chromatids are held together at the centromere - Humans have 46 chromosomes in all cells except sex cells o Arranged into 23 sets (homologous pairs) o 22 sets of autosomes o 1 set of sex chromosomes o Females are XX o Males are XY - Prokaryotes divide by binary fission - Actin protein around membrane contracts and pinches cell apart Cell Cycle How does the cell decide its time to divide? Regulatory factors Do cells live forever? Normal cells die… senescence Go through certain number of cell divisions and then die Cancer cells are immortal -Eukaryotic cell cycle Cytokinesis= cell division G1= growth S= DNA replication, synthesis phase G2= growth+preparation for mitosis M= mitotic phase Prophase Metaphase
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Anaphase Telophase *Then cycle begins again Mitosis Prophase
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This test prep was uploaded on 04/21/2008 for the course BIO 301L taught by Professor Wandelt during the Fall '07 term at University of Texas at Austin.

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BIO final exam - BIO final exam Replication -occurs in the...

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