Term
| What are the phases of the cell cycle? |
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Definition
| Go, G1, S, G2, M S is DNA replication |
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Term
| What enzyme does DNA replication? |
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Definition
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Term
| Where does DNA replication start from? |
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Definition
| the ORI (origin of replication) |
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Term
| In what direction does DNA replication occur form the ORI? |
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Definition
| It goes in both directions. It is called bidirectional replication. HOWEVER, DNA is always constructed 5' to 3'. |
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Term
| Can DNA be synthesized in a 3' to 5' manner? |
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Definition
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Term
| What does the term semi-discontinuous mean? |
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Definition
| It means that the lagging strand is synthesized in Okazaki fragments. |
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Term
| Are both strands of DNA replicated? |
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Definition
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Term
| What is the lagging strand? |
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Definition
| This is the strand that gets constructed with small segments of DNA called Okazaki fragments. The other strand (the leading strand) gets synthesized as one whole piece. |
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Term
| Do the leading and lagging strands conduct DNA replication at the same pace? |
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Definition
| YES! surprisingly enough they do |
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Term
| What enzyme ties okazaki fragments together? |
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Definition
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Term
| What happens to start DNA synthesis? |
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Definition
| OK. So the Origin of Replication Complex (ORC) binds. And DNA helicase starts to spread open the DNA's limbs to get it ready for action (haha no pun intended) |
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Term
| Where does regulation of DNA replication occur? |
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Definition
| at the level of ORC binding |
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Term
| What do topoisomerases do? |
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Definition
| They cut the DNA to relieve strain during replication and then they re-ligate it |
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Term
| What happens after the ORC binds? What enzyme does it? |
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Definition
| DNA Primase (part of DNA Poly alpha) puts down an RNA primer of 10 nucleotides. |
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Term
| After the laying down of RNA primer, what happens? |
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Definition
| DNA is extended from the primer 5' to 3' on the leading strand. On the lagging strand, they are kicked off by growing DNA. The RNA kinda hangs off like a flap and is cut off by flap endonuclease (FEN) |
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Term
| What does Replication Protein A do? |
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Definition
| It binds of ssDNA and keeps it from binding another strand. |
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Term
| Does DNA poly alpha do the whole DNA replication? |
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Definition
| No, DNA poly delta comes in and beasts it after about 20 NTs. Its better because it clamps onto DNA, so it works faster and adds more nucleotides before it falls off. |
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Term
| Drugs like AZT are nucleoside analogues. What does that mean? |
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Definition
| They are nucleosides, but they have a modification which allows them to stop the continuation of DNA synthesis, because phosphoester bonds can't happen with them. |
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Term
| If AZT has a high Km for human DNA polymerase and a low Km for viral DNA polymerase, what does that mean? |
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Definition
| It means that it has high affinity for viral DNA poly, and low affinity for human DNA poly. The AZT nucleotides won't be incorporated so easily into human DNA, so the human won't die. |
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Term
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Definition
| This is the end of the chromosome. It is repetitive and protects the chromosome from degradation. |
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Term
| What is the "end replication problem"? |
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Definition
| The last RNA primer cannot attach to the end of the LAGGING strand. SO, lose a bit of DNA with replication. Need to elongate, or the DNA will get shorter and shorter. |
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Term
| What solves the end-replication problem? |
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Definition
| Telomerase is a non-template DNA polymerase which adds the telomere at the end. It actually carries an RNA template and thus functions as RT. |
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Term
| How does telomerase work? |
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Definition
| It uses an RNA primer to extend the leading strand by RT activity. Then, DNA polymerase extends the lagging strand using the leading strand as a template. |
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Term
| What is special about the end of the leading strand after telomerase does its job? What does this do? |
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Definition
| Telomerase adds a 3' overhang which allows the telomere to loop over and bind to the rest of the DNA via complementarity. This is called T-loop and prevents the DNA from degradation. |
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Term
| Is Telomerase active in all cells? What is it called if it isn't active? |
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Definition
| No, telomerase is mainly active in rapidly replicating cells. Differentiated cells do not want telomerase, because they want to senesce to prevent cancer. Cancer cells have a lot of telomerase, so that they can just keep going and going like the energizer effing bunny. GREAT. |
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Term
| What is the most profoundly important thing about DNA replication? |
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Definition
| It is very boring and I hate molecules and cells. |
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