This document contains a recap of prokaryotic and eukaryotic DNA replication, transcription, translation, PTM, gene expression and expression regulation. It is a short recap you can use to learn about these topics or use it as a refresher for the BMR course Biotechnology.
For the summary/notes,...
Molecular biology single strand break repair (SSBR):
All cells on earth have DNA that is composedofy monomeric nucleotides:ATGC.
Base excision repair (BER)
living
Because they piece ofhuman DNAandinsertit Nucleotide excision repair (NER)
are all the same
you couldtake a into a
bacterium anditwill replicate. Each nucleotide consists ofa deoxiribose + phosphate group BER repairs non-helix distorting base lesions from the genome.
WER repairs bulkyhelix-distorting base lesions from the
+ a base (ATOC): genome, also called
DNAreplication initiation Non-homologous joining
end
Replication starts atthe
origin of replication (ORI. Homologous recombination
In the and for
prokaryotes replication occurs in the cytoplasm, eukaryotes in the
Non-homologous end
joining:break ends are directly
ligated andcan lead to
nucleus. Prokaryotes only contain one ORI as eukaryotes carry multiple. The translocations.
reason for this is faster replication, since the
genome is so
big. Thus,
prokaryotes have only
two replication forks and the replication is bidirectional, Homologous recombination:exchange of genetic information. These new DNA
forks combinations in the Iti s usedfor horizontal
Where as eukaryotes have multiple replication bubbles andmany replication represent offspring. also
gene
Replication in
prokaryotes is initiatedwhen DnaAbinds to the ORI and starts to transfer in bacteria andviruses, this is the mechanism for the spread of
separate the strands. DnaC Chelicase loader) interacts with DhaAand recruits DnaB antibiotic resistance in bacteria.
Chelicase), that continues unwinding the DNA. DnaG primace adds an RNAprimer HR uses 3'ssDNA overhangs thata re loaded with recombinase RAD51 (RecAin
polymerase prokaryotes) begins homologous (similar) sequence. The strand
andDNA III
holoenzyme begins elongation. and to look for a
In eukaryotes replication starts when the Origin recognition complex binds to the gets invaded, a forms
D-loop and
genetic information gets crossed -
over atthe
ORI. factors then recruited initiation complexforms. Hollidayjunction.
Replication are andan
The double helixis unwound by helicase andDNA polymerase a primace -> ds break
synthesises an RNA
primer. DNApolymerase 8 and a continue DNAreplication.
DNAreplication elongation 3.Resection
3 5'
5
In prokaryotes the DNAi s read in the 3's' direction. Therefore, the
3
lagging strand that is
heading away from the replication fork (s is
strand invasion
synthesisedin short Okazakifragments, requiring many primers. The RNA
m
D-loop
formation
primers eventually degraded by RNase H and
polymerase exonuclease.
DNA
-...
are
synthesis
DNA
The gaps/nicks are filledin with DNApolymerase in andsealedwith
ligase.
-
In similar but 8 is usedfor
eukaryotes the process is polymerase leading strand - . . . . . . . . .
8 and
synthesis and polymerase a for lagging-strand synthesis. Both polymerase a
contain 3's'
proofreading.
----------------- Branch,migrain Ar
in
DNAreplication termination
Prokaryote replication is terminatedwith the use of Tus proteins that lett he Transcription initiation
DNA copied into mRNAstrandwith the
replication forks only pass through one direction until theyeventually meet. is an use of RNA polymerase
The same happens in eukaryotes. Prokaryotic genes occur in operons, which are series genes
of that code for
In eukaryotes replication of chromosome ends poses a
problem, is
cause DNA the same protein andare controlled bya single promoter. Transcription is
lost from ends oft he chromosome each time the cell divides. This is where initiated when the o-factor binds to the -35promoter region (TTGACA) and
telomers come in. Telomerase makes a s's' RNAtemplate, reverse transcrip the DNAgets unwound at the -10 promoter region CTATAAT), forming a trans-
tase synthesises this to DNA. The RNA template is removed and the DNA forms cription bubble. The 5-factor core
+
enzyme together form the RNA
T-loop at the endofthe chromosome. Ashelterin cap is addedfor
protection.
a
polymerase holo enzyme.
In eukaryotes transcription is initiatedwhen general transcription factors (TFID,
Topoisomerase 1:to remove supercoils from the DNA, type I
topoisomerase cuts TFIA. TFIB, etc) bind to the promot er to form a preinitiation complex. The TATA-
strand, passing the other strand relaxes the
one
through, strand, and reanneals, boxi s a
recognition sequence for the TATAbox
binding protein CTBP) that
Topoisomerase 11:c uts both strands
simultaneously of which they
use ATP, to initiates the assembly ofthe transcription complexa tmanygenes. Eukaryotic
uncoil the DNA. It uses a "two-gate"mechanism for this.
genes also contain
cis-acting control elements that can bindactivators / enhancers
or repressors/silencers.
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