Genomics transmission of genetic information Flashcards
What does the sense strand have the same sequence as?
The sense strand has the same sequence as the mRNA molecule
What is the antisense strand used for?
The opposite, antisense strand is used as the template to
generate this identical mRNA strand
How is mRNA extensively modified after transcription?
-Capped at 5’ end
-Polyadenylated at 3’ end
-Introns removed
What is the central dogma?
DNA–>RNA–>protein
What happens in transcription?
- Transcription begins with strand of DNA with the transcription unit, which is used to create the RNA
- TFIID is a transcription factor, and a component of it called TBP, binds to the TATA box on the DNA. Other transcription factors like TFIIA and TFIIB will then attach.
- This is in preparation for the successful binding of RNA polymerase
- once RNA polymerase is bound, other transcription factors complete the mature transcription complex
- ATP is reduced to ADP and pi which allows RNy synthase to synthesise an RNA strand from the DNA strand.
- Once the end of the transcription unit is reached, the polymerase detaches and RNA formation is complete
What does 5’ capping protect?
-Protects 5’ end from degredation
What does 5’ capping facilitate transport into?
Facilitate transport into
cytoplasm
What does 5’ capping enhance?
Enhance translation
How many nucleotides are added in polyadenylation?
-50-250 nucleotides are added
What is not translated in genetic transmission?
Not the cap, not the UTR, not the polyA tail, only the RNA from the coding exons is translated
How is RNA read?
RNA “read” in threes = codons
How many possible combinations are there from the 4 bases?
64 possible combinations of 4 bases
What does a codon code for?
Codon → specific amino acid
What does it mean by open reading frame?
Same nucleotide sequence can be used
differently
Where does translation occur?
Cytoplasm
What happens to mRNA in translation?
mRNA to protein
What type of RNA is needed in translation and what does it carry?
Needs tRNA (transfer RNA)
-tRNAs carry amino acids
What are tRNA specific to?
Specific to codon
What do tRNA need?
-Needs initiation factors
-Needs elongation factors
What are the steps involved in translation?
- Translation initiation
- Translation elongation
- Translation Termination
What happens in translation initiation?
- mRNA binds to small subunit
-Ribosome binding site sequence binds to a complementary sequence in an RNA molecule in the small subunit of the ribosome, with the help of protein initiation factors - Initiator aminoacyl tRNA binds to start codon
- Large subunit of ribosome binds, completing ribosome assembly and translation begins
What happens in translation elongation?
- Incoming aminoacyl tRNA.
-New tRNA moves into A site, where the anticodon base pairs with the mRNA codon - Peptide bond formation
-The amino acid attached to the tRNA in the P site is transferred to the tRNA in the A site - Translocation
-mRNA is ratcheted through the ribosome by elongation factors. The tRNA attached to the polypeptide chain moves into the P site. The A site is empty. - Incoming aminoacyl tRNA
-New tRNA moves into A site, where the anticodon base pairs with the mRNA codon - Peptide bond formation
-The polypeptide chain attached to the tRNA in the P site is transferred to the aminoacyl tRNA in the A site - Translocation
-mRNA is ratcheted through the ribosome again. The tRNA attached to polypeptide chain moves into P site. Empty tRNA from P site moves to E site, where tRNA is ejected. The A site is empty again
What happens in translation termination?
- Release factor binds to stop codon
-When translocation exposes a stop codon, a release factor fills the A site. The release factor breaks the bond linking the tRNA in the P site to the polypeptide chain - Polypeptide is released and ribosome subunits seperate
-The hydrolysis reaction frees the polypeptide, which is released from the ribosome. The empty tRNAs are released either along with the polypeptide or when the ribosome seperates from the mRNA, and the 2 ribosomal subunits dissociate. The subunits are ready to attach to the start codon of another message and start translation anew.
