Lecture 4 Flashcards
What is transcription?
When we take the information encoded in gene in DNA and encode that information in mRNA.
How is the transcription in prokaryotic cells?
Starting with the DNA, from that you code the mRNA.
Then that mRNA can be involved with the ribosome, that that’s the Translation! So no processing happens after RNA polymerase does its job.
Where does the transcription happens in eukaryotic cells (structure)? How many steps (from what to what)?
Inside the nucleus.
Two steps:
From DNA -> to pre-mRNA
pre-mRNA -> to mRNA
which can then leave the nucleus and be translated into protein.
The primary actor in the transcription process starts with?
The RNA polymerase.
What does the RNA polymerase do?
It creates a sequence that will become a nucleotide sequence, then it will become the mRNA.
Where does RNA polymerase starts the process?
It attaches to a sequence of the DNA known as promoter.
Then it separates the strands.
After it can code for RNA.
How can the RNA polymerase function when separating the strands? (Hint. DNA replication)
Only to 5’ to 3’ direction by adding more nucleotides.
Template strand? Coding strand? Which one does RNA polymerase binds?
RNA polymerase binds to the template strand creating same pair as with the coding strand.
Where does the RNA polymerase stops?
'’Terminator’’ creates signals to the RNA polymerase that it’s time to stop.
So, the RNA polymerase has stopped its process and formed into ‘‘pre-mRNA’’. What happens next? (Only in eukaryotic cells)
At the start:
A 5’ cap, which is a modified guanine, which helps in the translation process.
At the end:
A 3’ end has a poly A-tail.
How does the pre-mRNA splicing happens?
Introns are spliced out, because they do not code for the protein.
So basically how does the pre-mRNA proccessing happens?
You add the 5’ cap, you add the 3’ end poly A-tail and exons between them.
How do you go from a gene to a protein?
From gene to mRNA. (transcription)
From mRNA to Protein. (Translation)
Where does the translation to a protein happen?
In a ribosome, where it will be translated into a polypeptide sequence.
What is ribosome made of?
Made up of proteins + ribosomal RNA (rRNA)
What does the ribosome do to the mRNA?
It travels along the mRNA, from the 5’ end to the 3’ end, reading it, and taking that information, turning it into a sequence of amino acids.
How does the reading of mRNA in ribosome happens?
Each of the three nucleotides, a codon (example AUG), the information is encoded in the nitrogenous bases.
How do we get from a codon to a specific amino acid? Amount of amino acids?
There are 22 standard amino acids, 21, found in eukaryotic cells. 64 permutations, so more than enough for coding for the amino acids.
61 codes for amino acids, 3 STOPS the process.
How does the amino acids bind together to form a polypeptide? How do they get matched with a right codon?
With transfer RNA (tRNA).
Each of the tRNA’s combine to a specific amino acid.
And with their anti-codons, the pair with the right codon.
How does the proper codon - tRNA combination chain actually forms?
With three steps:
From left to right:
E-site, P-site, A-site.
What is the A-site?
A-site is where the appropriate tRNA initially bounds to an amino acid.
What happens when the bound of a amino acid happens in the A-site?
You have a peptide bond form between the two amino acids, and the ribosome can move to the right. So the A-site goes to the P-site.
What are P- and E-sites?
P-site is where the polypeptide chain is actually formed.
E-site is ready to exit from the ribosome.
How does antibiotics work?
In prokaryotic cells in ribosomes we can find molecules that hurt the function of ribosomes.
The antibiotics can interrupt the translation process in the bacteria but not in the cells you want to keep.
