DNA polymerase δ has Polymerization activity and Proofreading 3´→ 5´ exonuclease activity.DNA polymerase γ synthesizes mitochondrial DNA.DNA polymerase β functions in DNA repair (it has 5´→ 3´ exonuclease activity).DNA polymerase α has a Primase activity (for the synthesis of RNA primer) Polymerization activity (formation of phosphodiester bond), and No proofreading 3´ → 5´ exonuclease activity.In eukaryotes, there are at least 5 DNA polymerase enzymes (α, β, γ, δ and ε ) The RNA-primed synthesis of DNA demonstrating the template function of the complementary strand parental DNA. The selection of the incoming deoxyribonucleotide is dependent upon proper base pairing with the template. The free 3´ hydroxyl group of the primer acts as an accepter for the first deoxyribonucleotide in the newly formed DNA strand.ĭNA polymerases utilize one deoxyribonucleoside triphosphate as a source of the deoxyribonucleoside monophosphate for the growing DNA strand by the removal of pyrophosphate. The primer provides a site for the polymerization to begin. oligonucleotide of RNA with free 3´ hydroxyl group), a template (i.e single-stranded DNA), and deoxyribonucleotides (d ATP, d CTP, d GTP, and d TTP) in order to function. Requirements of DNA replication in eukaryotesĭNA replication DNA is synthesized by DNA polymerasesĭNA polymerases require the presence of a primer (i.e. The additional accuracy is accounted for by a separate enzyme system that repairs the mismatched base pairs remaining after replication. Proofreading 3´→ 5´ exonuclease activity double- checks each nucleotide after it is added and removes the mispaired one. During cell division ( mitotic M phase), each daughter cell receives one of the two identical DNA molecules.ĭuring polymerization, discrimination between correct and incorrect nucleotides depends on base-pairing interactions (A=T and G≡C). This phase is preceded and followed by two periods during which DNA is not synthesized (gap periods G 1, and G 2). DNA replication occurs in the nucleus during the synthetic (S) phase of the eukaryotic cell cycle.Replication is very accurate: replication proceeds with an extraordinary degree of fidelity.Replication exhibits polarity: DNA synthesis proceeds in a 5´ → 3´ direction and is semi discontinuous.Having multiple origins of replication provides a mechanism for rapidly replicating the great length of eukaryotic DNA molecules. Replication begins at multiple origins and usually proceeds bidirectionally.DNA replication is semiconservative: Each DNA strand serves as a template for synthesis of a new strand producing two DNA molecules, each with one new strand and one old strand.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |