HW6().docx - 1 What is the origin of replication in DNA DNA...

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1. What is the origin of replication in DNA? DNA replication begins at a specific point in the DNA molecule called the origin of replication site. 2. Write the order of enzymes involved in the process of DNA replication. Helicase, primase, DNA polymerase III, DNA polymerase I, ligase 3. What is the direction of synthesis of leading and lagging strands? 5’ to 3’ 4. What is the role of RNA primer? If the primer attaches to DNA in 3’ to 5’ direction what will happen? Explain why? The RNA primer consists of a short sequence of RNA nucleotides, complementary to a small, initial section of the DNA strand being prepared for replication. Later the RNA primer is enzymatically removed and replaced with an appropriate sequence of DNA nucleotides. DNA polymerase can only add new nucleotides to a free 3’ end of a growing chain. Synthesis of one strand of the DNA, called the leading strand, proceeds continuously in the 5’ to 3’ direction. Synthesis of the complementary strand, called the lagging strand is more complex. DNA polymerase can add new deoxyribonucleotides only to a free 3’ OH. To provide a free 3’ OH starting point on the lagging strand, RNA primase attaches to the DNA and synthesizes a short RNA primer. DNA polymerase III then adds deoxyribonucleotudes to the 3’ end of the RNA primer. DNA polymerase I replaces DNA polymerase III, removes the RNA and replaces it with DNA. 5. How does a DNA ligase connect two lagging strands? The enzyme DNA ligase forms a phosphodiester bond between the 3’ OH of the growing strand and the 5’ phosphate in front of it.
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