BIOSC 0815 1st Edition Lecture 7Outline of Last Lecture I. Genea. NucleotideII. Nitrogenous Bases:a. Adenine, guanine. Cytosine, thymine.III. DNA StructureIV. DNA to chromosomesa. Chromatinb. Centromeresc. TelomeresV. DNA ReplicationOutline of Current Lecture II. DNA Replication Continueda. Origin of ReplicationIII. Steps of DNA Replicationa. Creating a Primerb. Polymerasei. Leading and Lagging strandc. LigaseCurrent Lecture- DNA Replication:o Parent DNA is acted on by lots of proteins with distinct functions Some recognize certain pieces of DNA (places to start replications) Open DNA Once the two strands are open there is a protein to hold the DNA open. Match up complementary bases Link pieces of DNA together.o Characters of replication: Nucleic Acids:- DNA (need to have a parental strand to copy from)- RNA (similar to DNA but single stranded) Nucleotides- A- TThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- C- G- U Proteins:- open DNA, unwind DNA, untangle DNA, Make a primer, Form DNApolymer,Link DNA togethero DNA strands are anti parallel: 5’ end is a phosphate group, 3’ end has a hydroxyl group. o Synthesis is always in the 5’ to 3’ direction. Always add nucleotides onto the 3’ end. o Origin of replication: Usually starts somewhere that there are lots of A – T pairs. They only have two H bonds so are easier to separate. There can be many origins.- Enzyme Steps:o Pry open the two strands of DNA with helicase. Breaks apart the hydrogen bonds. Helicase (breaks down helix).o Keeping it open: SSB (single stranded binding proteins to create two different strands of DNA).o Creating a Primer: RNA primer, beginning of new DNA Something that helps the process get started so that it can occur efficiently later on. (RNA uses u instead of T) RNA primase is what creates it.  Why? The enzyme that makes the polymer has to start with an existing 3’OH group. There’s nowhere for the DNA to begin unless there is a place to get started.  Now you have a 3’ OH group to begin adding nucleotides to.o DNA polymerase adds DNA nucleotides to the RNA primer. One strand gets added to in a smooth process. This is the leading strand On the other end it occurs in short stretches because it is going in the opposite direction. IT has to wait for the DNA to open up so that it can add another fragment. This is called the lagging strand. These fragments are Okazaki Fragments.  Get a discontinuous replication on lagging strand. They have to be put together somehow. o Ligase:  Puts together (links) Okazaki fragments with Ligase.o DNA polymerase replaces old RNA until everything is