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| Question | Answer |
| what is the role of the DNA replication fork? | the region of DNA at which all proteins involved in DNA replication come together to carry out synthesis of daughter strands (party central) |
| 2 strands of DNA replication | leading and lagging |
| leading strand | made continuously from a single RNA primer |
| lagging strand | made discontinuously- new primer made every few hundred bases |
| Okazaki fragments | 1. formed on the lagging template between 100 and 200 nucleotides long. 2. separated by ~10-nucleotide RNA primers and are unligated until RNA primers are removed |
| what maintains the stability of the replication fork? | single stranded binding proteins (RPA) - also stops ssDNA from being degraded by exonucleases |
| PCNA | 3 subunits form a circular structure through which DNA passes -maintains the stability of polymerase |
| bi-directional mechanism of DNA replication | two forks form at origin and move in opposite directions-both strands being copied in each direction |
| telomeres | repetitive sequence at end of chromosomes -protect from fraying |
| the 4 enzymes of DNA replication | 1. helicase, 2. DNA polymerase, 3. primase, 4. ligase |
| helicase | unwinds the double strand, this requires energy to break the H bonds |
| 3 DNA polymerase jobs | 1.copies the strand. 2. moves along the single strands and recruits dNTPs (nucleotide triphospates) to hydrogen bond their partners and helps build a second strand. 3. removes errors |
| primase | an RNA polymerase that is part of an aggregate of proteins called the primeosome. Attaches a small RNA primer to the ssDNA to act as a primer for synthesis (removed later by RNase H) |
| ligase | joins together two pieces of DNA when DNA polymerase I fills the gaps |
| what enzyme is responsible for synthesis? | DNA polymerase |
| 2 requirements for DNA polymerase to work | 1. needs a primer with a free 3'OH group, 2. it can only act 5'3' direction |
| DNA polymerase structure | highly conserved. The shape can be described as resembling a right hand with thumb, finger and palm domains. |
| why do we need DNA replication? | in order to copy chromosomes exactly before cell division to ensure new daughter cells have same content |
| origin of replication | the point at which the DNA unwinds and the primer binds, usually A-T rich regions |
| the DNA synthesied from the origin of replication is called | a replicon |
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