Cells can copy DNA double helices {replication, DNA}| {DNA replication}.
separation
Replication protein uses ATP to separate DNA nucleotide chains, by breaking hydrogen bonds between nitrogenous bases, so DNA unwinds. Replication protein starts at one DNA location and separates chains in both directions simultaneously. Single-strand binding protein keeps DNA strands apart.
pairing
RNA primer binds to operon first part and provides starting molecule to which DNA polymerase can add paired deoxyribonucleotides. Free deoxyribonucleotides hydrogen-bond with DNA-strand deoxyribonucleotides: A and T, or C and G.
linking
DNA polymerase links deoxyribonucleotides by phosphodiester bonds between pentoses, at rate 10 nucleotides per second. Pyrophosphate leaves. Copying error rate is only 10^-9. Exonuclease checks new strand at new deoxyribonucleotide pairs to see if deoxyribonucleotides paired correctly. Exonuclease removes wrongly paired nucleotides. Second exonuclease checks if double helix is correct and unwinds DNA if DNA double helix is not correct.
ligating
DNA ligase joins DNA strand ends. Both new strands link from ribose fifth carbon to next-ribose third carbon. One strand is continuous. One strand has Okazeki fragments. DNA ligase connects Okazeki fragments.
result
Replication makes two double helices, each with one strand of old double helix and one new strand {semiconservative replication, DNA}.
Replication protein uses ATP to separate DNA nucleotide chains, by breaking hydrogen bonds between nitrogenous bases {replication fork}, and so unwinds DNA.
Enzymes {replication protein} can use ATP to separate DNA nucleotide chains, by breaking hydrogen bonds between nitrogenous bases, and so unwind DNA.
Enzyme {single-strand binding protein} keeps DNA strands apart.
RNA primer binds to operon first part and provides a starting molecule for enzymes {DNA polymerase} that synthesize DNA from existing nucleic acid. It adds paired deoxyribonucleotides to DNA template strand and links them to make new strand.
Enzymes {DNA ligase} can join DNA strand ends and can rejoin broken DNA.
One strand forms in 1000-nucleotide segments {Okazeki fragment}. DNA ligase connects Okazeki fragments.
5-Chemistry-Biochemistry-Nucleic Acid
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Date Modified: 2022.0225