cap 11

dna replication

a process in which the original DNA strands are used as templates for the synthesis of new DNA strands.

template strands

parental dna strands

daughter strands

two newly made strands

conservative model

both parental strands of DNA remain together following DNA

replication.

semiconservative model

the double-stranded DNA is half conserved following the

replication process.

dispersive model

segments of parental DNA and newly made DNA are interspersed in

both strands following the replication process.

origin of replication

The site on the bacterial chromosome where DNA synthesis begins

bidirectionality

direction of replication

• The synthesis of new daughter strands is

  initiated within the origin and proceeds in both directions

replication fork

the region where the parental DNA strands have separated and

new daughter strands are being made

at rich region

where the DNA strands will initially separate.

dna a boxes

sequences that provide binding sites for DnaA proteins, which initiate the

formation of a replication fork.

gatc merhylation sites

provide a mechanism for regulating DNA replication

dna helicase

it breaks the hydrogen bonds between two strands of dna, thereby generating two single strands.

bidirectional replication

a phenomenon in which the bacterial chromosome is replicated in both directions

dna gyrase

an enzyme that travels in front of DNA helicase and relaxes positive supercoiling.

single strand binding proteins

bind to the strands of parental DNA and prevent them from re-forming a double helix.

rna primers

short strands of rna synthesized by the linkage of ribonucleotides via an enzyme

primase

synthesizes primers

lesding strand

a strand in which a single primer is made at the origin of replication.

lagging strand

a single strand in which multiple primers are made.

dna polymerase

responsible for synthesizing the DNA in the leading and

lagging strands.

dna polymerase III

responsible for most of the DNA replication during cell division

dna polymerase I

composed of a single subunit. Its

role during DNA replication is to remove the RNA primers and fill in the vacant regions with DNA.

epilepson

contains the 3’ to 5’ exonuclease site that removes mismatched nucleotides

okazaki fragments

DNA fragments

dna ligase

an enzyme that catalyzes the

formation of a covalent bond between adjacent Okazaki fragments to complete the replication process

in the lagging strand

primosome

DNA helicase and primase are physically bound to each other to form this protein complex

• tracks along the DNA,

  separating the parental strands and synthesizing RNA primers at regular intervals along the lagging

  strand.

replisome

The primosome is physically associated with two DNA polymerase holoenzymes to form this structure

dimeric dna polymerase

used to describe a complex of two DNA

polymerase holoenzymes that move as a unit during DNA replication

phosphodiester linkage

the linkage between a phosphate and two sugar molecules

processive enzyme

an enzyme that does not dissociate from the template strand after it has catalyzed the covalent joining of two nucleotides in

the growing daughter strand. Rather, it remains clamped to the DNA template strand and slides along that strand as it catalyzes the synthesis of the daughter strand

fidelity

a high degree of accuracy

proofreading function

The ability to remove mismatched bases.

• occurs by

  the removal of nucleotides in the 3′ to 5′ direction at the 3′ exonuclease site.

ars elements

many replication origins in a budding yeast

g quadruplex

G-rich sequences called G4 motifs. These motifs form a four-stranded helical structure termed this way

constitutive

Origins that are used all the time.

flexible

origins used in a random manner. These are the most common type.

dormant

origins used only at a specific stage of development or during cell differentiation.

prereplication complex

DNA replication in eukaryotes requires the assembly of this complex during the G1 phase of the cell cycle

origin recognition complex

acts as the first initiator of preRC assembly.

mcm helicase

ORC promotes the binding of Cdc6, Cdt1, and a group of six proteins called _____

dna replication licensing

The binding of MCM helicase to the leading strands completes this process

catenanes

two intertwined circular DNA molecules

dna gyrase

introduces a temporary break in the DNA strands and then rejoins them after the strands

have become unlocked.

dna polymerase alpha

the only eukaryotic polymerase that associates with primase. The functional role of this DNA polymerase primase complex is to synthesize a short RNA-DNA primer

polymerase switch

an exchange in which the DNA polymerase α/primase complex dissociates from the replication fork and is replaced by DNA polymerase ε or δ.

dna polymerase epilepson

involved with leading-strand synthesis.

dna polymerase delta

responsible for lagging-strand synthesis.

flab endonuclease

an enzyme that removes small RNA flaps that are generated by the action of DNA polymerase δ

telomere

telomeric repeat sequences within the DNA and the specific proteins that are bound to those sequences.

telomerase

an enzyme that catalyzes a specialized form of DNA replication that lengthens the telomere

telomerase rna component

the rna part of telomerase

• contains a sequence complementary to that found in the

  telomeric repeat sequence.

polymerization

a syntehsis in whichthe RNA sequence beyond the binding site functions as a template for the synthesis of a six-nucleotide sequence at the end of the DNA strand.

telomerase reverse transcriptase

Telomere lengthening is catalyzed by these two identical protein subunits of telomerase

senescent

when cells lose their ability to divide