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Genetics - Coggle Diagram
Genetics
Prokaryotic translation and transcription
overview
Prokaryotes lack a nucleus that is surrounded by a complex nuclear membrane
They contain smaller circular extracellular DNA called plasmids
Prokaryotes contain small amounts of non coding DNA
They have a single large circular chromosome that is located in the nucleoid
most prokaryotes are haploid
Protein syntehsis Transcription
Transcription
Elongation
A transcription bubble forms which moves along the holoenzyme
RNA polymerase moves form a 3' to the 5' direction and in the 5' to 3' direction - elongation.
RNA polymerase unwinds at the TATAAT site (rich in adenine and thymine)
mRNA is complementary to the template strand
Messenger RNA
MRNA is a product of transcription. It exists to encode information from the chromosomes into a readable format. it tells the ribosomes which amino acids to string together and in what order. MRNA is polyscistonic
Start and end codons AUG and UAA
Termination
1- terminaiton referes to the dissasociation of RNA polymerase form holoenzyme complexes formed form mRNA
2 - the point at which this coresponds to the end of the gene is signalled by the terminator
3- the termininators will form hydrogen bonds between base pairs of ssRNA creating a hairpin structure
What is Rho t
1 - the terminator contains a sequnece that embeds to a Rho binding site
2 - as the rho binds to the molecule , it will continue until it reaches the RNA polymerase
3 - Rho has helicase activity so it can promote the disassociation by unwinding DNA's double helix
Inititation
2 - RNA polymerase binds to the promotr region
3 - Association of sigma factors increase the binding affinity and specificity
1- RNA polymerase is the main transcriptional unit
RNA polymerase
RNA polymerase consists of different subunits - containing and alpha subunit and beta subunits. these will then associate with the sigma factor to form a holoenzyme
What are holoenzyme binding steps
they will bind to the 35 - box in the closely complex and they will also bind to the 10 . they will induce the formation of an open complex
Transcriptional initiation factors
Prokaryotic promotors have two characteristics that - they have the TTAGACG sequence (35 bases) which states where the starting point is
the TATAAT (10 sequence) tells you where the starting point is
Not all sigma factors are the same and they all serve an important role in intiation
Sigma factrors are regulated through the use of anti sigma proteins. they will typiucally bind to the sigma binding domain and a sensory/signalling domain on either within or without the cell.
it stabolises the sigma factor by binbinding ot the occluding RNA polymerase regognition sequnece
RseP senses the site clevage and then cleaves site 2 , resulting in a soluble sigma E/RSEA complex
Further cleavage results in degrated RSEA and sigma E bing released into the cytolasm
the outer membrane proteins that sense the stress and activate the DegS via the C terminal domain bind to PDZ , resulting in site 1 cleavage.
Overview - protein synthesis requires three major types of RNA - mRNA , tRNA and rRNA
Other types of RNA - there are other types of RNA - miRNA , siRNA and IncRNA and they all serve differernt functions
Protein sysntesis - Translation
Elongarion
2 - ribosome has 3 active site (A P E site)
3 - other proteins help this process along
1 - after initiation , the ribosome begins to read along the mRNA strand
Termination
What is Rho dependant termination
The termination step contains a sequence that encodes a Rho binding
It is thought that rho binds to mRNA and moves along the molecule until it reaches the RNA polymerase
Rho has helicase activity , so it thought to promote RNA polymerase dissociation
initation
it is comprised of rRNA and ribosomal proteins that are organised into large and small subunits
there are several initiation factor proteins that deliver proteins into smaller subunits to the mRNA
the ribosome is responsible for protein synthesis
prokaryotic mRNA contains shine-Dalgarno sequence that encodes robocall recognition binding
Prokaryotic translation
Elongation
Termination
Initiation
it is comprised of rRNA and ribosomal proteins that organise into a large and small subunits
Several initiation factors deliver the small units to the mRNA
The ribosome is the protein synthesis machine
the prokaryotic mRNA contains San Dalgarno sequence that encodes for a specific ribosomal and binding site
Transferee mRNA
tRNA transfers the amino acid form the growing peptide chain
the key features is that the 3' amino acid attachment site binds to the amino acid
the key feature is that the anticodon recognisees the codon on the mRNA
the correct amino acid must find the correct tRNA
aminoacytl tRNA synthetase
their job exists to match the correct amino acid to the correct tRNA
their is a specific aminoacyl-tRNA synthesise for each specific amino acid
aminoacyl-tRNA catalyses the attachement of the correct amino acid to tRNA
tRNA becomes charged
What is protein folding and polysomes
Once ribsosomes move away form the initiation site and bind to another
several ribosomes are translating a single mRNA strand and are at a single protozome
as the peptide chain grows it folds and gives it a three dimensional shape
Prokaryotic regualation
bacteria need gene regulation to respond to external stimuli
this is achieved through a two component regulator system
What is the lac operaon
The lac operon regulates gene expression in bacteria
They need a source of carbon like glucose for survival
they are a useful adaptation to enable the metabolism when they present in their environment