DNA replication Flashcards
Polymer consisting of deoxyribonucleoside
monophosphates covalently linked by
3’,5’-
phosphodiester bonds
(proteins with a
high content of arginine and lysine),
DEOXYRIBONUCLEOTIDE ACID
Located in the nucleus in eukaryotes and in the
nucleoid region of the cytosol in prokaryotes
DEOXYRIBONUCLEOTIDE ACID
Eukaryotic DNA is tightly bound to basic proteins called
histones
The process of disrupting the double helix is called
denaturation
denaturation
The two strands are
antiparallel
are highly repetitive sequences (TG-rich) at the
end of chromosomes
Telomeres
__ of cellular DNA is in mitochondria
1%
Biggest among the RNA
MESSENGER RNA (MRNA)
Copies genetic information from DNA and serves as the
template for protein synthesis
MESSENGER RNA (MRNA)
Methylguanosine cap at the 5’-end
* Poly (A) tail at the 3’-end
Methylguanosine cap at the 5’-end
* Poly (A) tail at the 3’-end
Contribute to the formation and function of ribosomes, which act as
the site for protein synthesis
RIBOSOMAL RNA (RRNA)
Most abundant RNA
RIBOSOMAL RNA (RRNA)`
are cleaved and modified by ribonucleases and
endonucleases to generate the required RNA species
Pre-rRNAs
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
Smallest among the RNA
TRANSFER RNA (TRNA)
Adapter molecules that translate the nucleotide sequence of
mRNA into specific amino acids
TRANSFER RNA (TRNA)
splicing post transcription
SMALL NUCLEAR RNA (SNRNA)
Small noncoding regulatory RNA termed micro-RNA (miRNA),
silencing RNA (siRNA) inhibit gene expression
Long noncoding regulatory RNA (lncRNA)
NONCODING REGULATORY RNA
Occurs during the S phase of the cell cycle
DNA REPLICATION
- Each strand serves as a template for complementary
daughter strand - Each strand becomes part of the daughter strand
Semi-conservative process
(proteins with a
high content of arginine and lysine),
DEOXYRIBONUCLEOTIDE ACID
Polymer consisting of
purine and pyrimidine
ribonucleotides linked
together by
3’,5’-
phosphodiester
bonds
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-
- Two newly made strands. The base
sequences are identical in both double-stranded molecules
after replication.
Daughter strands
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
- 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,
To complete the synthesis of Okazaki fragments along 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 - The covalent attachment of adjacent fragments of DNA
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
DNA helicase and primase bound to each other
DNA helicase and primase bound to each other
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
synthesizes DNA only in a 5′ to 3′ direction,
and it cannot link together the first two individual
nucleotides; it can elongate only preexisting strands.
DNA polymerase
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 telomerase RNA
component (TERC), contains a sequence complementary to
that found in the telomeric repeat sequence.
- Binding of Telomerase
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
