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cells15-DNA_ReplicationI-2009 - Bio 106 Cells Fall 2009...

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Unformatted text preview: Bio 106 Cells Fall 2009 Professor Owen 10/13/2009 Genes What do you know about the human genome project? Genes encoded in the DNA are translated into proteins ECB3 5-9 It’s your generation’s “trip to the moon” B. A pharmaceutical ploy to get government money C. We already knew everything about DNA – what’s the point? D. Never heard of it A. Desert and Coding Regions of the Human Genome NonNon-coding Sequences “Conserved” implies fundamental importance during evolution Each of the boxes represent a gene; the space in between is called the desert region “junk DNA”. Or is it? Surprisingly, the noncoding regions are highly conserved in mammals. Here, 14 mammalian species are compared. (CNGs = conserved non-genic sequences) (COD = protein coding regions) DNA Packaging Cell Cycle DNA is packaged on a spool and assembled into chromosomes. On the right, the 23 pairs of human chromosome have been arranged in a karyotype. Replication and segregation of chromosomes occurs through an ordered cell cycle. Cells spend most time in interphase. ECB3 5-10 ECB3 5-15 15- DNA Replication I 1 Bio 106 Cells Fall 2009 Professor Owen 10/13/2009 Essential DNA Elements Mitotic Chromosome Mitotic chromosomes contain contain 2 identical daughter DNA molecules (chromatids). ECB3 5-16 ECB3 5-17 ECB3 5-20, 21 Nucleosome DNA in interphase chromosomes is less compact Chromosome Chromosome Packing Chromatin is DNA associated with protein complexes. The The DNA winds around the protein spools. ECB Movie 5.2 ECB3 5-25 Proteins bind to the DNA – most abundant is the protein histone histone Histones pack the DNA into a structure called the nucleosome Histone proteins are extremely highly conserved The 30nm nucleosome structure is the most common packing of the interphase chromatin. Histones The nucleosome “spool” is an octamer, with two each of four different diff histone proteins locked in place by one molecule of H1. Cooper 5.12 Review: What did Avery’s experiment show? RNA is the genetic material B. Bacteria causes disease C. DNA is the genetic information that transformed bacteria D. Heat kills bacteria A. 15- DNA Replication I 2 Bio 106 Cells Fall 2009 Professor Owen 10/13/2009 ChromatinChromatin-remodeling Complexes DNA Replication Our cells constantly make new DNA … Complementary Basepairing 5’ 3’ If a segment of one DNA strand has bases: 3’---ATATCCG---5’ then the complementary strand should be: 5’ 3’ Complimentary basepairing allows each strand to be a template to make a new double strand identical to the original strand. 2 3’---ATATCCG---5’ B. 5’---ATATCCG---3’ C. 5’---TATACCG---3’ D. 5’---TATAGGC---3’ E. 3’---TATAGGC---5’ A. Modified from ECB 5-6 DNA acts as its own template Each old strand is copied to make a new helix with one old (orange) and one new (red) strand. “semiconservative” DNA Replication Fork ECB3 6-5 ECB3 6-2,3 15- DNA Replication I 3 Bio 106 Cells Fall 2009 Professor Owen 10/13/2009 DNA Replication Fork DNA Replication In the electron microscope, we can see that DNA replicates in more than one place at a time. Newly synthesized strands have opposite polarity ECB3 6-11 High High Energy Nucleosides Nucleosides are activated by the addition of inorganic phosphates from 2 ATPs. DNA Synthesized 5’ to 3’ Direction Addition of nucleoside triphosphates occurs at the 3’ end by the enzyme DNA DNA polymerase. ymerase. Energy for addition comes from release of two phosphate groups. ECB3 3-41 ECB3 6-10 A Problem … Since the two strands of DNA run in opposite directions, continuous synthesis of two new strands at the replication fork would require that one strand be synthesized in the (wrong) 5’ to 3’ direction. The Replication Forks Are Asymmetric Leading-strand Lagging-strand 15- DNA Replication I 4 ...
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