DNA REPLICATION Flashcards
initiated by the binding of DNAa protein to the origin of replication
REPLICATION
As the DNAa binds with DNAa binding sites, it
will cause the separation of a region (MELTED REGION - AT-rich region)
segment of DNA that replicates from a single origin of replication
REPLICONS
Prokaryotic replication
single replicon
Eukaryotic Replication
multiple replicons
the process by which a cell makes an identical copy of its DNA before cell division. It is a complex and highly regulated process involving multiple enzymes and proteins.
DNA REPLICATION
DNA replication begins at specific sites in the DNA molecule called
origins of replication
Attached to single strand; breaks the hydrogen bonds between base pairs, and thereby unwind the strands; this action generates positive supercoiling ahead of each replication fork
DNA HELICASE
It prevents the reannealing of DNA strand
Single-stranded Binding Proteins
It alleviates supercoiling by inducing cuts
DNA gyrase (toipoisomerase II)
DNA Replication produces
two identical DNA molecules, each consisting of one original strand and one newly synthesized strand
RNA primers are synthesized by an enzyme
Primase;
These primers are complementary to the DNA template and provide a starting point for DNA synthesis.
TRUE OR FALSE
Leading strand is towards the 3’ to 5’ direction.
TRUE
TRUE OR FALSE
Lagging strand is away the origin of replication.
TRUE
Primers are typically about ————— nucleotides long.
10-20 NUCLEOTIDES LONG
Main enzyme of DNA replication
DNA polymerase III
It attaches to the template strand forming replisome
DNA pol
DNA Synthesis on the Leading Strand:
On the leading strand, DNA polymerase synthesizes the new DNA strand continuously in the
5’ to 3’ direction
DNA Synthesis on the Lagging Strand:
On the lagging strand, DNA polymerase synthesizes the new DNA strand discontinuously in the form of short fragments known as
Okazaki fragments
needed at the start of each Okazaki fragment to provide a 3’ end for DNA polymerase to extend
RNA primers
The gaps between the newly synthesized DNA fragments on the lagging strand are sealed by an enzyme called
DNA ligase
removes the RNA primers and replaces them with DNA nucleotides on the lagging strand
DNA polymerase I
DNA ligase forms __——————————————___________________________________ between adjacent nucleotides, creating a continuous strand of DNA on the lagging strand
phosphodiester bonds
end product of replication
2 IDENTICAL DNA MOLECULES
Binds to ter sequences and prevents the advancement of the replication fork
TUS
Aid DNAa in the recruitment of DNA helicase in the origin
DNAc proteins
EUKARYOTIC DNA polymerase
DNA polymerase that has an exonuclease activity
gamma γ
delta δ
epsilon ε
EUKARYOTIC
synthesizes the RNA primer, initiations DNA synthesis and lagging strand
alpha
EUKARYOTIC
REPAIR DNA
beta and epsilon
EUKARYOTIC
Replicate mitochondrial DNA
GAMMA
EUKARYOTIC
Synthesizes the leading strand, filling DNA gaps after removal of primer
delta
PROKARYOTIC
Exonuclease activity from 3’ to 5’
DNA pol I and III
Additional DNA repair mechanisms exist to fix any remaining mistakes such as fixing the topological state of the DNA via
DNA gyrase (topoisomerase 3)
2 models of replication
- Theta Model
- Rolling Circle Model
new DNA strand is cut, and the mispaired nucleotide and its neighbor is removed. The missing patch is replaced with correct nucleotides by a DNA polymerase.
MISMATCH REPAIR
The unmatched base is removed, leaving a baseless nucleotide. The hole is filled with the right base.
BASE EXCISION REPAIR
dimer is detected, and the surrounding DNA is opened to form a bubble. Enzymes cut the damaged region, and the DNA polymerase replaces the excised DNA.
NUCLEOTIDE EXCISION REPAIR
Contains a telomerase RNA that serves as template for telomere elongation
TELOMERE REPLICATION
