Zoology101: Animal BiologyLast Lecture Outline Lecture 9 1. What Happens in the ER• Process of protein 2. What happens in the Golgi?3. Lysosomes4. Cytoskeleton 5. Peroxisomes 6. Mitochondria and chloroplast7. Evolution of Eukaryotic Cell Current Lecture 1. Finish up from last lecture; DNA2. Getting Started Finish Up from Last Lecture; DNA• Extracellular matrix: largely composed of glycoprotein; for structural support and anchorage for cells • DNA: sugar phosphate backbone • Polynucleotide strand (nucleic acid)• Nucleotide: pentose, phosphate group and nitrogenus groupDNA RNABases ATGC AUGCSugar Deoxyribose RiboseNumber of strands 2 1Location in cell Nucleus Nucleus; cytosol• Number the carbons on the sugars• A nucleic acid has directionality • 3prime end has hydroxyl group attached (can have replication)• 5prime end has phosphate group • DNA polymerase: enzyme that synthesizes new DNA strands, can only bind to the OH on the 3 prime• Double stranded helix: connected by hydrogen bonds • Specific base-pairing: complementary base pairing (A-T has 2 H bonds) (G-C has 3 bonds)• Two strands are anti parallel (run in opposite directions, i.e escalator) • Basic concept of DNA replication (Copying DNA)◦ When does it occur? Only right before cell division◦ Where? Nucleus (cannot fit through nuclear pores) ▪ Separation of strands (each one serves as a template▪ Daughter molecule forms; same nucleotide sequence as parent Getting Started • Origins of replication: sites within short stretches of DNA having specific enzyme sequence • A-T is the easiest to rip apart due to less H bonds → more pairs • Come together to form 2 strands• Bacteria only have 1 strand of circular DNA• Helix opens at Origins of Replicaiton • First, helicase unwinds the double helix at the H bonds between complementary nucleotides • Topoisomerase deals with the super coiling caused by the untwisting helix• Single stranded binding proteins stabilize each strand so that they don't recombine • DNA polymerase needs an OH on the 3 prime end in order to start forming DNA◦ Primase adds RNA primer (short stretch of RNA; 10-20 base pair nucleotides) that provides 3 prime OH for DNA polymerase • DNA polymerase III can make a DNA strand complimentary to template• Bottom strand is made in pieces (Okazaki fragments); on lagging/discontinuous strand (top strand is continuous, leading strand) • DNA polymerase I removes the RNA primers, fill in gap with DNA nucleotides• DNA ligase- Makes phospodiester bonds to seal the last little portion
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