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| A mold for the synthesis of complementary DNA |
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| S serves as a template for S, S' serves as a template for S' |
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| proteins that carry out DNA replication with extreme accuracy |
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| Semiconservative model of DNA replication |
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| each daughter DNA ends up with one of the original strands and one new strand |
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| The point at which DNA is opened up initially |
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| Purpose of beginning replication at many places in humans |
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| beginning replication at many places (~10,000) shortens time to copy entire genome |
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| Y shaped junctions where the replication machine (composed of proteins) moves along DNA |
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| enzyme that synthesizes DNA from 3’ to 5’ (forms phosphodiester bonds) |
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| Asymmetrical replication fork |
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Definition
problem with the 3’ to 5’ strand
(1) DNA polymerase can only synthesize in the 5’-3’ direction (adding subunits to 3’)
(2) Lagging strand (5’ to 3’) is synthesized in discontinuous Okazaki fragments |
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(2) Can correct mistakes in base-pairing through proofreading
(a) Takes place at the same time as DNA synthesis
(b) Before next base pair is matched, previous one is checked
(c) 3’ – 5’ proofreading carried out with different domain of polymerase (in the 5’ – 3’ direction) |
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Definition
| RNA primer. Needed to begin DNA synthesis by pairing to the template strand and providing a base paired 3’ end to start polymerase |
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| – synthesizes RNA using DNA as a template |
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| forms base pair with A in RNA (replaces T in DNA) |
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| to form a continuous DNA strand. Removes the RNA primer and replaces with DNA |
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| joins the 5’ phosphate end of one DNA fragment to the 3’ hydroxyl end of the next |
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Definition
Proteins acting together
Powers the replication fork forward and synthesizes new DNA behind |
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Definition
uses energy from ATP hydrolysis to lead the machine
unzips the helix |
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| Single stranded binding protein |
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Definition
| clings to single strand of DNA preventing it from recoiling |
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Definition
| keeps polymerase firmly attached to template |
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Definition
assembles the sliding clamp (hydrolyzes ATP each time clamp is locked)
Done once on leading strand and before every Okazaki fragment |
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| uses an RNA template part of the enzyme to replenish the nucleotides lost by adding the short sequence to the end. |
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| permanent problem in DNA. Have profound consequences. |
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Definition
leaves a mispaired nucleotide behind. Corrected 99% of the time
Aids in cancer prevention
Distinguishes between DNA strands |
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Definition
| “missing teeth” effect, purine bases (A and G) are lost during spontaneous reactions - does not break the phosphodiester backbone |
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Definition
| spontaneous loss of an amino acid group from cytosine in DNA to produce the base Uracil |
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Term
| Nonhomologous recombination |
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Definition
| When damage is done to both strands - Repair by nonhomologous end-joining mechanism which rejoins broken ends via DNA ligation - nucelotides usually lost at repair sites |
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Term
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Definition
Both complementary strands are compromised – repairs DNA based off an entirely different, yet similar, strand
o A nuclease generates single stranded ends at the break by chewing back one of the complementary DNA strands
o Using enzymes, one single strand invades the homologous DNA duplex by forming base pairs with the complementary strand |
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Term
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Definition
where 2 DNA strands (1 from each duplex) cross
Where the invading strand is elongated by a repair DNA polymerase using the complementary strand as a template
‘Migrates’ as duplexes separate. Repair is completed by DNA synthesis and DNA ligation
Result = 2 intact helices |
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Definition
| Site of genetic exchange - responsible for genetic diversity during meiosis |
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| in bacteria. responsible for genetic diversity |
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Term
Mobile genetic elements
"Jumping genes" |
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Definition
changes that alter the order of genes on a chromosome or add new info
o Short segments of DNA that can move from one position in the genome to another
Usually can’t leave the cell |
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Definition
| can escape from one cell and infect another – genes encased by a protein coat – need to enter a cell to replicate their chromosomes and use machinery |
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| only in eukaryotes – DNA synthesized using RNA as a template |
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| passed on copy of a virus (HIV) |
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| aka mobile genetic elements. Classified by the mechanism in which they move. |
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| unique to eukaryotes, move via an RNA intermediate (ie: L1 element ~15% of the genome) |
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| enzyme that makes a DNA copy of RNA intermediate |
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| copies the nucleotide sequence into RNA |
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| enzymes that carry out transcription - Can start an RNA chain without a primer |
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Definition
| RNA that specifies the AA sequence of proteins |
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| form the core of the ribosome and catalyze protein synthesis |
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Definition
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| serve as adaptors between mRNA and AA during protein synthesis |
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Definition
| process by which info encoded in DNA sequence is translated into a product that has some effect on a cell or organism |
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| Initiation of transcription |
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Definition
| where a cell can select which proteins or RNAs are to be produced and at what rate |
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Definition
o Asymmetrical – can only synthesize in one direction (5’ – 3’)
o A segment of DNA will only be transcribed if preceded by a promoter sequence
o Binds to promoter, opens up double helix
o One exposed DNA strand acts as the template for complementary base pairing |
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Definition
| area that the enzyme recognizes and attaches to the double helix |
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Definition
| point where polymerase stops and releases DNA and new RNA chain |
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| Sigma Factor (in bacteria) |
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Definition
| responsible for recognizing the promoter sequence of DNA – unbinds after recognition |
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| General transcription factors |
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Definition
| assembles at each promoter along with polymerase before polymerase can transcribe |
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Definition
| takes place as RNA is transcribed in order to transport RNA out of the nucleus |
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| Modification of the 5’ end of mRNA (synthesized 1st) by capping with a G nucleotide with an attached methyl group |
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Definition
Gives mRNA a poly-A tail (series of Adenines) on the 3’ end
why?
Increase stability of mRNA molecule and aid in its export from the nucleus and to identify molecule as mRNA |
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Definition
| expansive areas of noncoding, intervening sequences |
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| scattered pieces of coding sequences, expressed sequences |
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Introns removed, exons stitched together
Sequences that are similar in all introns mark them for removal by RNA molecules |
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