| A | B |
|---|
| Prokaryotic replication occurs | in the cytoplasm |
| Eukaryotic replication occurs | in the nucleus |
| DNA replication occurs in | S phase |
| purpose for DNA replication | to duplicate chromosomes, so that after mitosis each daughter cell will inherit a complete genome |
| Non-dividing cells | blocked in Go do not progress to S phase |
| Exonuclease | 3' to 5' exonuclease activity excises mismatched nucleotides |
| Direction of DNA replication | 5'->3' |
| origins of replication (ori) | Replication proceeds in both directions from here |
| Okazaki fragments | discontinuous, lagging strand replicated as short stretches |
| Semiconservative | One strand of a daughter chromosome is newly replicated, the other template strand is inherited intact from the parental chromosome |
| DNA replication is what? | Semiconservative |
| DNA Polymerase | enzyme that catalyzes polymerization of dNTPs into DNA |
| Prokaryotes have how many DNA polymerases? | 3 |
| Eukaryotes (us) have how many DNA polymerases? | 4 |
| Found in nucleus, leading strand replication, has proofreading, uses RNA primer | Pol (epsilon) |
| Found in nucleus, lagging strand replication, has proofreading, has RNA primer | Pol (delta) |
| Found in nucleus, fills in gaps, no proofreading, no RNA primer | Pol (beta) |
| Found in mitochondria, replicates, no RNA primer both strands, has proofreading, | Pol (gamma) |
| Cofactor needed for DNA polymerase activity, not incorporated into DNA | Magnesium (Mg2+) |
| To replicate a new strand, DNA polymerase ___ | Must read preexisting strand called a template |
| Just as active as S phase | G1 and G2 (***) |
| Deoxyribonucleotides (dNTPs) | building blocks of DNA, all four required for replication |
| NTPs produce | RNA |
| lack 2 hydroxyls | dNTPs- deoxy |
| Deoxyguanosine and deoxycytidine base pair with | 3 H bonds |
| thymidine and deoxyadenosine base pair with | 2 H bonds |
| What provides energy for nucleotide polymerization? | Hydrolysis of the triphosphate bonds |
| Energy is stored in the triphosphate bonds as what in dNTPs? | electrostatic repulsion of negatively charged oxygens |
| Nucleotide Hydrolysis. 3' has___ and 5' has___ | OH group, Phosphodiester bond |
| The last requirement for DNA replication is | Primer |
| A free hydroxyl group at the 3' position of the terminal nucleotide of a previously existing strand. | primer |
| Have to add a new nucleotide to the | 3' end |
| DNA polymerase can only form a phosphodiester bond between | 3'OH and 5' phosphate of an incoming nucleotide |
| always adds in the | 5' to 3' direction |
| : the template is in the opposite orientation (antiparallel), so it is read | 3'-5' direction |
| because no polymerase can replicate 3' to 5' direction | its added in a Discontinuous pattern |
| Okazaki Fragments are made in the direction | 5'-3' |
| Ori ( Origins of Replication) | sequence where DNA replication begins |
| Unwinds the DNA, final step of initiation | Helicase |
| Single Stranded Binding Proteins | Bind to unwound strands and Inhibit from forming double helixes |
| Replisome | on each side of Ori |
| Replisome | Assembles around helicase to replicate DNA. Moves in opposite directions |
| Primase | RNA polymerase that transcribes the primer (3'OH) |
| Sliding Clamp | ring like protein, secures strands to Pol (Epsilon) and Pol ( (Delta). Increase Processivity |
| Clamp Loader | Loads sliding Clamp |
| DNA Polymerase (Delta) | uses the RNA primer to replicate an Okazaki fragment. |
| DNA Polymerase (Epsilon) | Replicates leading strand, reads template one base at a time. |
| DNA Polymerase (Epsilon) | Binds 5' phosphate to 3' OH of the growing leading strand |
| Topoisomerase | Helps restore DNA to proper level of supercoiling |
| RNAase | digests RNA, removes lagging strand primers |
| DNA Polymerase (Beta) | Fills in short gaps left after RNA primers are removed |
| DNA Ligase | binds free 3' hydroxyls and 5' hydroxyls of DNA. Seals the Nicks left by Pol (beta) |
| DNA polymerases can only do what? | Add nucleotides, |
| DNA polymerase (Beta) leaves behind something | Nicks in the DNA |
| Telomerase | RNA primer is removed, leaves overhang. This keeps the chromosome from being degraded by exonucleases |
| Telomerase is a | reverse transcriptase, fills in gaps and extends the length of telomeres |
| Telomerase activity | decreases with age along with telomere length |
| Primary cell culture lines divide limited number of times | believed because they have no telomerase activity |
| Immortalized cell culture lines | can divide indefinitely |
| Telomerase is activated in | cancer cells, which contributes to their immortalization |
