ZOL 141 1st Edition Lecture 4 Outline of Last Lecture I II III IV V Genes and Genomes Macromolecules DNA RNA Nucleic Acids Made of nucleotides Polynucleotides Outline of Current Lecture I DNA Replication II Leading and Lagging Strand III DNA replication enzymes Helicase and DNA polymerase IV Chromosomes V Organization of DNA in Chromosomes Current Lecture DNA Replication Semiconservative model Conservative model Dispersive model Works in ONLY one direction 5 3 So new nucleotides added to 3 end Substrate molecule added to DNA strain for DNA synthesis dATP dCTP dTTP dNTP OH group bids to 5 phosphate of incoming nucleotide 2 phosphates cleaved of nucleotide linked to nucleic acid chain Leading and Lagging Strand leading strand synthesized continually lagging strand synthesized discontinually DNA replication enzymes Helicase and DNA polymerase Helicase unzipping enzyme opens up DNA breaks hydrogen bonds DNA polymerase puts in correct nucleotides Chromosomes Threadlike structure in nucleus Linear end to end arrangements of DNA wrapped around proteins Carry genetic info Ultimately define structure and function of each cell Chromatin DNA and protein components visible as clumps or threads Humans have 46 chromosomes in somatic cells 2n 46 23 pairs n 23 Homologous chromosomes o Pair of chromosomes carrying identical gene loci o 44 autosomes or 22 pairs o two sex chromosomes female XX Male XY What is a Chromosome o One chromatid one DNA molecule o Contain Centromere and Telomere Organization of DNA in Chromosomes Chromatin DNA and protein components of chromosomes Total length of DNA in one cell 2 meters 6 5 feet Needs to fit into nucleus tight packing Wraps around histones
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