Term
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Definition
| A y-shaped region of each replication bubble, where new DNA strands are elongating |
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Term
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Definition
| untwist the double helix at replication forks |
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Term
| Single-strand binding protein |
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Definition
| keeps DNA single stranded, to be used as a template |
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Term
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Definition
corrects "overwinding" ahead of replication forks by breaking, swivelling and rejoining DNA strands
corrects overwinding, it cuts the sugar phosphate backbone periodically, races ahead of replication fork and snips the strands which is later on repaired. |
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Term
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Definition
| Makes a primer which primes DNA replication... lays down a short stretch of RNA (5 to 10 nucleotides long) to provide a primed hydroxyl group so DNA polymerase can do its work |
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Term
| DNA polymerases cannot ______ by they can add nucleotides to the ____ end. |
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Definition
| initiate synthesis of a polynucleotide, 3' |
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Term
| Does the enzyme primase require a primer? |
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Definition
| no, it can make RNA from scratch, so it can add RNA nucleotides using parental dNA as a template |
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Term
| DNA polymerase adds nucleotides in what form? |
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Definition
| as a nucleoside triphosphate |
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Term
| What supplies adenine to DNA? |
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Definition
| dATP.... the difference between dATP and ATP is that the first one has deoxyribose while ATP has ribose |
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Term
| What does the structure of dATP look like? |
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Definition
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Term
| What does the structure of ATP look like? |
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Definition
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Term
| As each monomer of dATP joins the DNA strand what happens? |
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Definition
| they lose 2 phosphate groups as pyrophosphate |
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Term
| What type of structure does the double helix have? |
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Definition
| an antiparallel structure in which the two strands are oriented in opposite directions (this affects replication) |
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Term
| a new DNA strand can only elongate in which direction? |
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Definition
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Term
| what direction is the leading strand in? |
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Definition
the direction that the DNA polymerase wants, and is always following the replication fork
unlike the lagging strand where DNA polymerase must work in a direction away from the replication fork 5’ to 3’ on the template
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Term
| Okazaki fragments are joined together by what? |
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Definition
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Term
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Definition
Chemicals
and radioactive emissions |
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Term
| Nucleotide excision repair |
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Definition
| when in the sun UV causes dimerization of neighbouring thymines (they join together, neither of them base pair properly which causes a mutation in the double helix...forms skin cancer!) |
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Term
| The 5' can't finish off because we have linear chromosomes, you can't go beyong it to set up a primer. What regulates this problem? |
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Definition
The end of our chromosomes have long repeat sequences called telomeres. They do not code for anything so it doesn't matter if you shorten it.
Some cells like cancer cells don't have this problem because of telomerase enzyme which is a built in primer that extends the telomere |
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