Chapter 11_DNA Replication Flashcards
Template Strands
(Parental Strands) During the replication process, the two complementary strands of DNA come apart and serve as template strands for the synthesis of two new strands of DNA.
After the double helix has separated…
…individual nucleotides have access to the template strands.
To complete the replication process…
…a covalent bond is formed between the phosphate of one nucleotide and the sugar of the previous nucleotide.
Daughter Strands
The two newly made strands after replication.
Semiconservative Model
The double stranded DNA is half conserved following the replication process. In other words, the newly made double stranded DNA contains one parental strand and one daughter strand.
Origin of Replication (oriC)
The site on the chromosome where DNA synthesis begins
DNA replication is initiated by…
…the binding of DnaA proteins to seuqences within the origin known as DnaA box sequences.
Which bonds are stronger, the AT or GC region?
The GC. Because only two hydrogen bonds form between AT base pairs, whereas three hydrogen bonds occur between G and C, the DNA strands are more easily separated at an AT-rich region.
- DnaA protein
- DnaC protein
- DnaA protein: Binds to DnaA boxes within the origin to initiate DNA replication
- DnaC protein: Aids DnaA in the recruitment of DNA helicase to the origin
Dna helicase (DnaB)
Separates double-stranded DNA
Topoisomerase
(Type II, or DNA gyrase) Removes positive supercoiling ahead of the replication fork
Single-strand binding protein
Binds to single-stranded DNA and prevents it from re-forming a double-stranded structure
Primase
Synthesizes short RNA primers
DNA polymerase III
Synthesizes DNA in the leading and lagging strands
DNA polymerase I
Removes RNA primers, fills in gaps with DNA
DNA ligase
Covalently attaches adjacent Okazaki fragments
Tus
(Termination Utilizatino Substance) Binds to ter (termination sequences) sequences and prevents the advancement of the replication fork
RNA primers
They start, or prime, the process of DNA replication.
- Leading Strand
- Lagging Strand
- Leading Strand: A single primer is made at the OriC
- Lagging Strand: Multiple primers are made.
DNA Polymerase I, II, III, IV, V
- I and III are involved in normal DNA replication
- II, IV, and V play a role in DNA repair and the replication of damaged DNA.
To complete the synthesis of Okazaki fragments within the lagging strand, three additional events must occur:
Removal of the RNA primers, synthesis of DNA in the area where the primers have been removed, and the covalent attachment of adjacent fragments of DNA.
Fidelity
DNA synthesis occurs with a high degree of accuracy or fidelity.
Proofreading function
Occurs by the removal of nucleotides in the 3’ to 5’ direction at the 3’ exonuclease site.
Describe differences between prokaryotic and eukaryotic DNA replication
- Prokaryotic: One OriC.
- Eukaryotic: Multiple OriC
ARS elements
(Autonomously replicating sequences) Replication origins that are necessary to initiate chromosome replication. They contain a higher percentage of A and T bases.
Prereplicatino complex
(preRC) DNA replication in eukaryotes begins with the assembly of a preRC. Part of the preRC is a group of proteins called the origin recognition complex (ORC) that acts as the initiator of eukaryotic DNA replication.
MCM helicase
The binding of MCM helicase at the origin completes a process called DNA replication licensing.
Flap endonuclease
Removes small pieces of RNA flaps that are generated by thea ction of DNA polymerase.
Telomerase
Prevents chromosome shortening. It recognizes the sequences at the ends of eukaryotic chromosomes and synthesizes additional repeats of telomeric sequences.
