9-RNA Transcription & Translation Flashcards
Which is the flow of genetic information?
DNA→RNA→protein
Where does translation take place?
In ribosomes (cytosol)
Where does transcription takes place?
In the nucleus
What is the function of the ribosomal RNA (rRNA)?
It is a structural component of ribosomes
What small nuclear RNA (snRNA) consist of?
RNA and proteins
From which side of a tRNA is the amino acid located?
It is located in the 3’ end
How does a polypeptide start and end?
It starts with an amino gorup (H3N) and finishes with a carboxyl grouo (COO-)
Does the mRNA come out of the nucleus maturated or not?
It comes out maturated.
What is alternative Splicing?
It is like the original ‘splicing’process. However in this case except from the introns, an exon can be rremoved too, so a different protein is created. It is an answer to the question: How is it possible that there are millions of human
antibodies when there are only about 30,000 genes
What is a Poly-tail and where can be found?
It is a sequence that protects the mRNA from degradation, it can be found in the 3’ end of an mRNA:
- It aids in the export of the mRNA to the cytoplasm
- Is involved in binding proteins involved in initiating translation
What is a Cap and where can be found?
It can be found in the 5’ end of a mRNA molecule.
- Protects the new-made mRNA from degradation
- Iniatiation factors involved in translation recognise the cap to help initiate translation by ribsosomes
How many are the codons and the amino acids?
64 codons and 20 amino acids.
**There are 61 codons for 20 amino acids
( 3 codons are stop signals and they do not correspond to any amino acids)
These codons are universal, what does this mean?
That these codons appear in all living organisms
How many fates does a codon have?
It has 3 fates:
- Initiate translation
- Code an amino acid
- Terminate translation
How many sites does a large ribosomal unit have and which are their function?
A large ribosomal unit has two sites ( A and P site):
A site: Is the site where the amino acids will wait in order to be linked to the peptide chain.
P site: Is the site for the growing polypeptide chain
How many and which parts does translation have?
It has 3 parts:
- Initiation
- Elongation
- Termination
What happens in the initiation part of the translation?
The initiation phase of protein synthesis requires
over 10 eukaryotic Initiation Factors (eIFs): Factors
are needed to recognize the cap at the 5’end of an
mRNA and binding to the 40s ribosomal subunit.
▪Binding the initiator Met-tRNAiMet (methionyltRNA) to the 40S small subunit of the ribosome.
▪Scanning to find the start codon by binding to the 5’cap of the mRNA and scanning downstream until they find the first AUG (initiation codon).
▪The start codon must be located and positioned correctly in the P site of the ribosome, and the initiator tRNA must be positioned correctly in the same site.
▪Once the mRNA and initiator tRNA are correctly bound, the 60S large subunit binds to form 80s initiation complex with a release of the eIF factors.
In which direction do the amino acids move during elongation?
They move from the A to P site in order to be connected with the polypeptide chain.
What does the termination state of a translation process require in order to occur (signals)?
It requires a stop codon and specifing releasing factors (RFs)…………..eRFs in euakryotes.
How final proteins are formed?
Polypeptides fold spontaneously into their active
configuration, and they spontaneously join with other
polypeptides to form the final proteins.
What type of mileculesa can be attached to proteins?
-sugars
ilipids
-phosphatases etc…
All of these have a special function to the protein.
What proteolytic enzymes are? Name a category of them and the enzymes this category consists of.
Proteolytic enzymes are aenzymes that cleave proteins. One category is the serine proteases that include dugestive enzymes:
- trypsin
- chymotrypsin
- elastase
Where does chymotrypsin prefer to cut?
prefers an aromatic side chain on the residue whose carbonyl carbon is part of the peptide bond to be cleaved
Where does Trypsin prefer to cut?
Trypsin prefers a positively charged Lys or Arg residue at this position.
What do lysosomes contain?
contain a large variety of hydrolytic enzymes that degrade proteins & other substances taken in by endocytosis.
What is ubiquitination?
Is the process in which proteins are tagged for selective destruction by covalent attachment of ubiquitin
What is ubiquitin?
It is a small, compact, highly conserved protein.
Are all proteins degraded by after ubiquitination?
no
How ubiquitins are attached to each other? (bonds)
Carboxyl group- ε-amini group of Lys29 or Lys48 residue.
What proteasomes are and where do they function in?
They are responsible for protein degradation and they function in the cytosol and the nucleus.
What does the proteasome complex consist of?
The proteasome core complex, with a 20S sedimentation coefficient, contains 2 each of 14 different polypeptides.
7 a-type proteins form each of the two a rings, at the ends of the cylindrical structure.
7 b-type proteins form each of the 2 central b rings.
Which are the “categories” of mutations?
- harmful
- lethal
- helpful
- silent
