Week 2 Flashcards
What underlies the production of all cellular proteins?
Translation of mRNA into polypeptides.
How are 20 amino acids encoded in the genetic code?
Four bases in RNA/RNA encode 20 amino acids.
DNA RNA Protein
4 nt 4 nt 20 AA
What are the building blocks of proteins?
Amino acids
What are non-polar amino acids?
are hydrophobic (often in the core of proteins, where they avoid water)
What are the characteristics of amino acids with polar side chains?
are hydrophilic (tend to be on outside of proteins) By interacting with water they make proteins soluble
What does the amino acid sequence lead to?
leads to proteins having a 3D structure
What do proteins make up?
Hair and nails Blood Brain and nerves Enzymes cellular construction workers. Antibodies Cellular messengers Muscles
What does a triplet code offer?
64 combinations
What are the properties of the genetic code?
Triplet
Non-overlapping
Non-ambiguous
Genetic code is degenerate (each AA encode by more than one codon).
What is the primary structure of a protein?
Sequence of a chain of AA.
What is the secondary structure of a protein?
Hydrogen bonding of the peptide backbone causes the AA to fold into repeating pattern.
What is the tertiary structure of a protein?
3D folding patterns of a protein due to side chain interactions.
What is the Quaternary structure of a protein?
Protein consisting of more than one AA chain.
What does translation involve?
involves to specialised types of RNA.
What is rRNA?
Ribosomal RNA
Forms a molecular machine that conducts translation.
Large and small subunits
What is tRNA?
Transfer RNA.
Carries specific AA into the ribosome during translation
Has a feature called an anticodon.
Where is translation performed?
Ribosome
What does a ribosome have?
has a small and a large subunit
Each subunit is made of proteins and ribosomal RNA (rRNA)
What does a 1/3 of the ribosome contain?
1/3 of mass of the ribosome is protein
Proteins on the exterior
What do rRNA catalyse?
rRNA molecules catalyse the formation of the peptide bond between amino acids
Two of the three domains populated exclusively by ______.
prokaryotes
In the third domain _____ multicellular life is largely restricted to ____ recent branches ____, ____, _____.
Blank 1-(Eukarya)
blank 2-three
Blank 3- (fungi, plants, animals)
What does the anti-codon correspond with?
The codon in order to form AA.
What do all proteins start with?
the amino acid Methyonine (M)
What do the subunits do when attached to an mRNA molecule?
The small and large ribosomal subunits assemble when attached to an mRNA molecule
Translation initiation complex
What is the P-site?
peptidyl site), binds to the tRNA holding the growing polypeptide chain of amino acids.
What is the A site?
(acceptor site), binds to tRNA holding the new amino acid to be added to the polypeptide chain.
What is the E site?
exit) binds a tRNA that already unloaded its amino acid and it is going to be released.
What is termination?
A release factor binds directly to the stop codon in the A site
Addition of H2O molecule instead of an amino acid
What is the process of termination?
1) Ribosome reaches a stop codon on mRNA.
2) Release factor promotes hydrolysis.
3) Ribosomal subunits and other components dissociate.
In Prokaryotes when is mRNA translated into proteins?
In prokaryotes mRNA is translated into protein as soon as it is made
Because transcription and translation happen in the same place.
How is mRNA translated into proteins in eukaryotes?
In eukaryotes mRNA has to be transported out of the nucleus before it can be translated
What do both transcription and translation have in common in eukaryotes and prokaryotes?
In both cases several ribosomes can simultaneously translate one mRNA molecule
What is a consequence of having a genetic code?
Reading frames
What is a open reading frame?
Start with the AUG start codon
End with one stop codon, UAG, UAA or UGA (U in mRNA, T in DNA).
What are operons in bacteria?
Region of DNA containing a cluster of genes under the control of a single promoter
How can the genes within the operon be activated?
All the genes of the operon can be activated with a single transcription factor
What is the lac operon?
Bacterial operon to metabolise lactose (sugar)
Repressed if there is glucose
Active if there is lactose
What happens when there is no lactose present?
When lactose is absent the lac repressor binds tightly to the operator. It gets in RNA polymerase’s way, preventing transcription.
What happens when there is lactose present?
Rearranged lactose binds to the lac repressor and makes it let go of the operatoe. RNA polymerase can now transcribe the operon
What do prokaryotes organise?
organise genes into operons- unit containing several genes involved in the same metabolic pathway.
What do eukaryotes typically control?
Eukaryotes typically control expression of individual genes rather than operons like prokaryotes
What are there many levels of?
Many levels of regulation!!! From chromatin packing to post-translational modifications of the end protein
what are the multiple scales of regulation of gene expression?
Epigenetic Transcriptional Post-transcriptional Translational Post-translational
What is Transcriptional?
Modify the rate of gene transcription using transcriptional enhances upstream of the promoter.
what is meant by Post-transcriptional?
Stability of mRNA, alternative splicing.
what is meant by Translational?
speed of translation
what is meant by Post-translational?
modification of protein
What do transcription factors recognise?
recognize and bind to double stranded DNA
What can transcription factors be?
They can be activators or repressors
What do transcription factors do?
will bind to DNA which will signal the RNA polymerase to start transcription.
What do individual transcription factors do?
regulate the expression of many genes
Why are Transcriptional cascades important?
are important for signal transduction and environmental adaptation
Outline the steps of the transcription cascade.
Distribution of information within cells and genomes
Sequencing of several steps of gene expression over time
Amplification of a weak signal from a cell surface receptor