DNA replication Flashcards by Jasmine Tabangcora

Polymer consisting of deoxyribonucleoside
monophosphates covalently linked by

3’,5’-
phosphodiester bonds

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(proteins with a
high content of arginine and lysine),

DEOXYRIBONUCLEOTIDE ACID

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Located in the nucleus in eukaryotes and in the
nucleoid region of the cytosol in prokaryotes

DEOXYRIBONUCLEOTIDE ACID

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Eukaryotic DNA is tightly bound to basic proteins called

histones

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The process of disrupting the double helix is called

denaturation

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The two strands are

antiparallel

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are highly repetitive sequences (TG-rich) at the
end of chromosomes

Telomeres

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__ of cellular DNA is in mitochondria

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Biggest among the RNA

MESSENGER RNA (MRNA)

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Copies genetic information from DNA and serves as the
template for protein synthesis

MESSENGER RNA (MRNA)

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Methylguanosine cap at the 5’-end
* Poly (A) tail at the 3’-end

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Contribute to the formation and function of ribosomes, which act as
the site for protein synthesis

RIBOSOMAL RNA (RRNA)

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Most abundant RNA

RIBOSOMAL RNA (RRNA)`

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are cleaved and modified by ribonucleases and
endonucleases to generate the required RNA species

Pre-rRNAs

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Prokaryotes have 50S and 30S subunits, made up of 3 types of
rRNA:

Eukaryotes have 60S and 40S subunits, made up of four types
of cytosolic rRNA:

16S, 23S, and 5S

18S, 28S, 5S, 5.8 S

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Smallest among the RNA

TRANSFER RNA (TRNA)

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Adapter molecules that translate the nucleotide sequence of
mRNA into specific amino acids

TRANSFER RNA (TRNA)

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splicing post transcription

SMALL NUCLEAR RNA (SNRNA)

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termed micro-RNA (miRNA),
silencing RNA (siRNA) inhibit gene expression

Long noncoding regulatory RNA (lncRNA)

NONCODING REGULATORY RNA

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Occurs during the S phase of the cell cycle

DNA REPLICATION

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Each strand serves as a template for complementary
daughter strand

Semi-conservative process

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Polymer consisting of
purine and pyrimidine
ribonucleotides linked
together by

3’,5’-
phosphodiester
bonds

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The two
complementary strands of DNA that came apart. Hydrogen
bonding between individual nucleotides and the template
strands must obey the AT/GC rule.

Template strands or parental strands-

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Two newly made strands. The base
sequences are identical in both double-stranded molecules
after replication.

Daughter strands

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Both parental strands of DNA remain together following DNA replication

* Conservative model-

the original arrangement of parental strands is completely conserved,

* Conservative model-

The double-stranded DNA is half conserved following the replication process.

Semiconservative model-

Proposes that segments of parental DNA and newly made DNA are interspersed in both strands following the replication process.

Dispersive model-

origin of Chromosomal replication, is where DNA synthesis begins

Origin of replication (oriC)-

Three types of DNA sequences are found within oriC:

an AT-rich region, DnaA box sequences, and GATC methylation sites.

- site where the parental DNA strands have separated and new daughter strands are being made

Replication fork

The replication of the bacterial chromosome in both directions, is an event termed

bidirectional replication.

sites within oriC are involved with regulating DNA replication.

GATC methylation

begins with the binding of DnaA proteins to sequences within the origin of replication known as DnaA boxes.

DNA replication

are more easily separated at AT-rich region.

DNA strands

Break the hydrogen bonds between base pairs and thereby unwind the strands; this action generates positive supercoiling ahead of each replication fork.

DNA helicase-

Travels in front of DNA helicase and alleviates positive supercoiling.

Topoisomerase II (DNA gyrase)-

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

Single-strand binding proteins-

Short strands of RNA typically 10–12 nucleotides in length. start, or prime, the process of DNA replication.

RNA primers-

Synthesize the RNA primers

Primase-

* Leading strand- Single primer * Lagging strand- Multiple primers

responsible for synthesizing the DNA along the leading and lagging strands.

DNA polymerase-

Involved in normal DNA replication

Polymerase I and III-

Responsible for most of DNA replication

Polymerase III-

DNA repair and replication of damaged DNA

Polymerase II, IV, V-

toward the opening of the replication fork.

Leading strand-

n away from the replication fork.

Lagging strand-

repeatedly initiate the synthesis of short segments of DNA; the synthesis is

discontinuous.

DNA fragments named after __ and ____ who initially discovered them in the late 1960s.

Reiji and Tsuneko Okazaki,

the RNA primers are removed by the action of DNA polymerase I.

Lagging strand-

Catalyzes a covalent bond between adjacent Okazaki fragments to complete the replication process in the lagging strand

DNA ligase-

DNA helicase and primase bound to each other, forming

primosome

Perimosome and 2 DNA polymerase holoenzymes

Replisome-

used to describe two DNA polymerase holoenzymes that move as a unit during DNA replication.

Dimeric DNA polymerase-

origin of replication (ori) is recognized by a group of proteins called

origin recognition complex (ORC)

unwinds the double helix, in a process that is driven by ATP

Helicase

relieve torsional strain that results from helicase-induced unwinding

Topoisomerases

synthesizes short segments of complementary RNA primers

Primase

elongates the DNA strand by adding new deoxyribonucleotides

DNA polymerase III

is synthesized continuously

Leading strand

consists of Okazaki fragments

Lagging strand

fills the gap with deoxyribonucleotides

DNA polymerase I

seals the nick by catalyzing the formation

DNA ligase

E. coli chromosome from oriC is a pair of termination sequences, known as

ter sequences.

the nucleotide about to be attached to the growing strand is a

deoxyribonucleoside triphosphate (dNTP).

It contains three phosphate groups attached at the 5′ carbon (C) atom of deoxyribose.

deoxyribonucleoside triphosphate (dNTP).

The dNTP first enters the catalytic site of DNA polymerase and binds to the template strand according to the

AT/GC rule.

group on the previous nucleotide reacts with the phosphate group

3′ hydroxyl (—OH)

adjacent to the sugar on the incoming nucleotide.

(PO4 2−)

The formation of this covalent bond causes the newly made strand to

grow in the 5′ to 3′ direction.

hydrogen bonding between G and C or between A and T is much more stable

Stability of Base Pairing

DNA polymerase can identify a mismatched nucleotide and remove it from the daughter strand.

Proofreading

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

Proofreading

appears to be substantially more complex.

eukaryotic DNA replication

functions in the mitochondria to replicate mitochondrial DNA

DNA polymerase γ

are involved with DNA replication in the cell nucleus.

α, ε, and δ

is the only eukaryotic polymerase that associates with primase.

DNA polymerase α

an enzyme that removes successive nucleotides from the end of a polynucleotide molecule

exonuclease

is involved with leading-strand synthesis.

DNA polymerase ε

is responsible for lagging-strand synthesis.

DNA polymerase δ

have the primary function of replicating DNA.

α (alpha), ε (epsilon), δ (delta), and γ (gamma),

is primarily responsible for RNA primer removal.

flap endonuclease

are needed so the DNA can be replicated within a reasonable length of time.

multiple origins of replication

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

* Telomeres

cannot be replicated by DNA polymerase because a primer cannot be made upstream from this point.

The 3′ end of a DNA strand

prevents chromosome shortening. It recognizes the sequences at the ends of eukaryotic chromosomes and synthesizes additional repeats of telomeric sequences.

Telomerase-

The 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.

Polymerization

The RNA part of telomerase, known as __, contains a sequence complementary to that found in the telomeric repeat sequence.

telomerase RNA component (TERC)

Telomerase then moves to the new end of the DNA strand and attaches another six nucleotides to the end.

Translocation

tend to shorten with age.

Telomeres

When telomeres are too short, the cells become ____, which means they lose their ability to divide.

senescent