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DNA replication

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dejucefa's version from 2017-04-13 17:42

prokaryotes

Question Answer
synthesis of new DNA strands is catalyzed by DNA polymerase III
what determines the nucleotide sequence of the new DNA strand?base pairing with template strand
what is the source of energy used to syhthesize new DNA?hydrolysis of phosphates attached to deoxyribonucleotide that's being added to the strand
DNA polymerase reads template strands in what direction?3' --> 5'
DNA polymerase assembles new strands in what direction? adding to what end?5' --> 3'. adds to 3' end
what are the 2 functions of DNA polymerase?catalyzing DNA synthesis, checking each deoxyribonucleotide & removing incorrect base pairs
where does DNA replication start?replication initiation site, where proteins separate 2 strands and allow replication complex to assemble
what is the function of DNA primase?to form DNA primer, which is necessary for synthesis initation on leading strand
what is a replisome?replication complex, large group of associated enzymes
what is the function of DNA helicase?part of replisome, separates 2 DNA strands, energy from hydrolysis of ATP
what is the leading strand?first new strand formed by leading strand DNA polymerase
what is the lagging strand?strand being formed in segments, its replicatoin lags behind the leading strand
what are Okazaki fragments?short DNA fragments formed on lagging strand (about 200 nucleotides long)
base pairing of the lagging strand is slower becauseeach segment must be initiated by RNA primer, so there's a new strand with a free 3' end
what is the function of single-strand DNA binding protein?binds to & protects exposed single-stranded regions of lagging-strand DNA
what is the function of DNA primase?synthesizes RNA primer
what is a RNA primer?RNA segment complementary to DNA template, about 10 nucleotides long
what is the function of lagging strand DNA polymerase IIIadds deoxyribonucleotides to the 3# end of RNA primer until it contacts the 5' end of the next RNA primer
what is the function of DNA ligase?joins free ends of Okazaki fragments
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eukaryotes

Question Answer
what enzyme catalyzes lagging strand DNA synthesis?DNA polymerase alpha
what enzyme catalyzes leading strand DNA synthesis?DNA polymerase delta
what enzyme catalyzes mitochondrial DNA synthesis?DNA polymerase gamma
in which direction do polymerases read template DNA strands?3' to 5'
in which direction do polymerases assemble new DNA strands?5' to 3'
when an acid sequence is written out, assume that it starts at the ___ end unless it says otherwise5'
where does initiation occur on the DNA of mature body cells?replication initiation sites / replication origins
where does initiation occur on the DNA of oocytes & early embryos?many sites, irrespective of DNA sequence
during what cell phase does DNA replication occur?S phase, synthesis#
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prokaryotes & eukaryotes

Question Answer
what is the general function of topoisomerase enzymes?prevent twisting, tangling & interlocked loops of DNA
what is the function of type I topoisomerases?temporarily clip one strand to allow untwisting
what is the function of type 2 topoisomerases?cut both strands to allow second double-stranded heliz to pass through
what types of organisms use photoreactivation?prokaryotes & plants
what types of organisms use base excision repair?all
what types of organisms use nucleotide excision repair?all
what is the function of DNA photolyase?catalyzes photoreactivation, uses light energy to remove covalent bonds joining pyrimidines into dimers (pyrimidine dimers produced by UV light)
what is the function of glycosylase?removes damaged bases from deoxyribose
what enzyme carries out nucleotide excision repair?DNA polymerase
how does nucleotide excision repair work?nucleotides are removed & replaced by new strand, based on methylation of older strand
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