Replication DNA (Chapter 11) to form new chromosomes DNA must be copied copying DNA is called "replication" each strand used as a template to form complementary strand .
DNA Replication DNA must make exact copy of itself every cell division must result in same DNA semi-conservative replication accepted form of DNA replication in contrast with other models conservative, dispersive .
Fig. 11.1 Three models for the replication of DNA
Peter J. Russell, iGenetics: Copyright Pearson Education, Inc., publishing as Benjamin Cummings.
Replication of DNA nucleotides are added one by one DNA polymerase enzyme that mediates this reaction reaction progresses from one end to other (like a zipper unzipping) .
Fig. 11.4a DNA chain elongation catalyzed by DNA polymerase
Peter J. Russell, iGenetics: Copyright Pearson Education, Inc., publishing as Benjamin Cummings.
Replication of DNA replication has multiple points of origin along strand of DNA replication fork region where strands are separating initiation process of starting a new replication fork initiation takes place simultaneously at several points along the DNA strand .
Replication of DNA multiple initiations along DNA strand allows replication to occur more quickly movement of each replication fork ~ 10 to 100 nucleotides per second ordinary cells - ~ 15 to 30 minutes for chromosomes to fully replicate .
Replication of DNA role of DNA polymerase enzyme that directs replication process requirements for DNA polymerase to direct DNA replication template strand must exist 5'triphosphates of the 4 deoxyribonucleotides must exist must be a primer
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Fig. Diagram of the formation at a replication origin sequence of two replication forks that move in opposite directions
Peter J. Russell, iGenetics: Copyright Pearson Education, Inc., publishing as Benjamin Cummings.
Fig. 11.13 Temporal ordering of DNA replication initiation events in replication units of eukaryotic chromosomes
Peter J. Russell, iGenetics: Copyright Pearson Education, Inc., publishing as Benjamin Cummings.
Replication of DNA primer strand short of nucleic acid actually a segment of RNA (ribonucleic acid) in living cells primer is required for initiation each strand is replicated from 5' to 3' end .
Direction of replication always from 5' to 3' one strand can replicate continuously other strand must replicate in pieces leading strand strand that replicates continuously lagging strand strand that replicates in pieces fragments called precursor or Okazaki.
Replication of DNA primers segments of nucleic acid that start at initiation points in most cells primer is strand of RNA RNA ribonucleic acid single stranded instead of double uracil instead of thymine ribose instead of deoxyribose synthesis of RNA requires RNA polymerase .
Replication of DNA Sequence of events DNA chain is opened RNA polymerase synthesizes an RNA primer primer segment joins to DNA template DNA polymerase synthesizes DNA fragments to attach to the primer and to the DNA template joining of fragments requires DNA ligase (enzyme that joins pieces of DNA) RNA primers ejected and replaced by DNA fragment .
Replication of DNA numerous proteins are involved in replication topoisomerase nicks and unwinds DNA in preparation for replication helicase unwinds DNA at replication fork single strand bindin...