ZOL 141 1st Edition Lecture 4 Outline of Last LectureI. Genes and GenomesII. MacromoleculesIII. DNA/RNAIV. Nucleic Acids: Made of nucleotidesV. PolynucleotidesOutline of Current Lecture I. DNA ReplicationII. Leading and Lagging Strand III. DNA replication enzymes: Helicase and DNA polymeraseIV. ChromosomesV. Organization of DNA in ChromosomesCurrent LectureDNA 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 chainLeading and Lagging Strand - leading strand synthesized continually- lagging strand synthesized discontinuallyDNA replication enzymes: Helicase and DNA polymerase- Helicase: “unzipping enzyme” opens up DNA, breaks hydrogen bonds- DNA polymerase: puts in correct nucleotidesChromosomes- 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 chromosomeso Pair of chromosomes carrying identical gene locio 44 autosomes or 22 pairso two sex chromosomes (female= XX, Male= XY)- What is a Chromosome?o One chromatid=one DNA moleculeo Contain Centromere and TelomereOrganization 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
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