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Gene Expression - Coggle Diagram
Gene Expression
Replication
Enzyme that forms these bonds
DNA polymerase
Energy source to form these bonds
Hydrolyzing the triphosphate into a monophosphate as the phosphodiester bond is formed
Bond type between monomers
phosphodiester
template
DNA
Begins at the origin on the template
Reactants (monomers)
deoxyribonucleotide
Basic Steps in the process
Helicase binds DNA at the replication origin. 2. Helicase unwinds DNA. The single stranded DNA is protected by single strand DNA binding proteins (ssDNA BPs).
Primase synthesizes an RNA primer so that polymerase has something to add on to.
DNA polymerase extends the primer to create DNA. The sliding clamp holds DNA polymerase onto DNA so it doesn't fall off. The leading strand proceeds continuously, but the lagging strand is made in pieces (Okazaki fragments). Each new fragment needs a new RNA primer.
When DNA polymerase runs into an RNA primer, it displaces it.
DNA ligase seals the DNA strands (makes a phosphodiester bond between them, this requires ATP hydrolysis).
Telomerase completes DNA replication of chromosome ends.
*Throughout the whole process, if DNA is overtwisted ahead of the helicase, topoisomerase makes a little cut, lets the DNA untwist, and then it is sealed back together
Product
DNA
Proceeds to completion
Processing/folding required before the product is ready for use
packaged on histones during DNA replication
Transcription
Bond type between monomers
phosphodiester
Enzyme that forms these bonds
RNA polymerase
template
DNA
Energy source to form these bonds
Hydrolyzing the triphosphate into a monophosphate as the phosphodiester bond is formed
Reactants (monomers)
ribonucleotides
Begins at the transcription start site (right after the promoter)on the template
Product
RNA
Basic Steps in the process
At the gene itself (the promoter, just before the transcription start site):
General transcription factors bind the gene promoter on DNA. Promoters are directional, so this identifies the DNA template strand for transcription. 2. RNA polymerase binds to the transcription factors and to DNA.
Meanwhile, at the enhancer:
Gene-specific transcription factors bind the enhancer on DNA. Enhancers are not located directly next to the gene, they are elsewhere in the DNA sequence, usually on the same chromosome
After both of these series of events are complete... 3. Mediator binds to the general transcription factors at the prommoter and the gene-specific transcription factors at the enhancer.
RNA polymerase begins to unwind DNA and RNA polymerase is activated via phosphorylation of its carboxy tail. (meaning the amino acids that stick out at the C terminus).
RNA polymerase begins synthesizing RNA at the transcription start site of DNA.
Transcription ends when RNA polymerase reaches the terminator.
Ends at the terminator region on the template
Processing/folding required before the product is ready for use
polyadenylation (addition of the tail)
splicing
capping
export from the nucleus
Translation
Ends at the stop codon on the template
Begins at the start codon on the template
Energy source to form these bonds
breaking the bond that joins the amino acid to the tRNA (forming that bond originally requires energy from ATP hydrolysis)
Basic Steps of the process
Translation initiation factors bind to mRNA as it exits the nucleus.
Different translation initiation factors help the initiator tRNA (the anticodon to the start codon, carrying the amino acid methionine) bind to the small subunit of the ribosome.
mRNA binds to the small subunit of the ribosome. 4. The ribosome scans the mRNA until the initiator tRNA is base paired with the start codon on mRNA. 5. The large subunit of the ribosome binds, positioning that initiator tRNA in the P site.
The next tRNA comes, base pairing with the mRNA in the A site.
The peptide bond forms between the amino acid in the P site and the amino acid in the A site. The whole polypeptide is still attached to the tRNA in the A site.
The ribosome slides down one codon on the mRNA.
The free tRNA that already lost its amino acid is now in the E site and exits.
Repeat steps 6-9 until there is a stop codon in the A site.
Release factor base pairs with the stop codon on mRNA, breaking the bond that holds the polypeptide to the tRNA in the P site and ending the process.
Enzyme that forms these bonds
Ribozymes/Ribosomal Enzymes (rRNA)
Bond type between monomers
peptide
template
mRNA
Reactants (monomers)
amino acids
product
Polypeptide (which folds into a protein)
Processing/folding required before the product is ready for use
folding
sometimes formation of disulfide bonds and other modifications before the protein is ready to function