Eukaryotic DNA replication Jackson Chary

1. Eukaryotic DNA Replication
Molecular Biology
Jackson Chary
M.Sc. BT (1st SEM)

2. Replication:
It is a process in which
the DNA copies itself to
produce identical
daughter molecules of
DNA
Occurs only once in one
cell
Replication of DNA
occurs based on the
Chargaff's Rule

3. Steps:
-Initiation (formation of --Pre-Replicative complex)
-Initiation Complex
-Elongation
-Termination

4. It is the first step in which most proteins combines to form Pre-
Replicative complex (Pre-RC
Involved proteins:
Origin Recognition. Complex(ORC)
Cell division cycle6 (CDC 6)
Chromatin licensing and DNA Replication factor1 (Cdt1)
Minichromosome Maintenance Protein complex (Mcm 2-7)

5. Steps in Initiation:

8. GINS complex is composed of four small proteins
Sld5 (Cdc105)
Psf1 (Cdc101)
Psf2 (Cdc102)
Psf3 (Cdc103)
GINS represents go, ichi, ni, san Which means
5,1,2,3 in Japanese

9. Elongation
After initiation complex is formed cell pass into S phase, then complex becomes
a replisome and elongation is initiated
Once elongation is initiated , it forms replication fork by unwinding the DNA
strand.
As double helix DNA separates from one side an super coils are formed on the
other side.
It is solved by DNA topoisomerase

10. Replication Fork:
This is the junction between the separated template strands and the
double stranded DNA
Elongation occur in 5` to 3` direction in both the leading and lagging
strand.

13. The leading strand is a single DNA strand that, during DNA
replication, is replicated in the 3' – 5' direction (same
direction as the replication fork). DNA is added to
the leading strand continuously, one complementary base
at a time
The lagging strand is synthesized in short, separated segments. On
the lagging strand template, a primase "reads" the template DNA
and initiates synthesis of a short complementary RNA primer. A DNA
polymerase extends the primed segments, forming Okazaki
fragments.

14. Three DNA polymerases are required
for eukaryotic genome replication: DNA
polymerase alpha (Pol α), DNA
polymerase delta (Pol δ) and DNA
polymerase epsilon (Pol ε) (1). Pol α
initiates DNA synthesis on both the leading and
lagging strands by synthesizing
a RNA/DNA hybrid primer.

15. Sources:
https://pubmed.ncbi.nlm.nih.gov/28301743/
https://bio.libretexts.org/Bookshelves/Introductory_and_General
_Biology/Book%3A_General_Biology_(Boundless)/14%3A_DNA_St
ructure_and_Function/14.3%3A_DNA_Replication/14.3C%3A_DN
A_Replication_in_Eukaryotes

16. @Jackson chary