Genes and proteins Flashcards
With what does he central dogma of molecular biology deal?
The detailed residue-by-residue transfer of sequential information.
What does the central dogma state?
Information cannot be transferred back from protein to protein or nucleic acid.
What is the genotype?
The genetic make-up of an individual.
What is the phenotype?
The physical traits.
Characteristics expressed by individual.
Why do regulatory systems and pathways interact?
To form complex networks.
What do complex networks add to most G-P maps?
Additional complexity.
Fr what does genotype code?
Phenotype.
What did George Beadle and Edward Tatum suggested in 1941?
Genes act through enzyme production.
Each gene is responsible to produce a single enzyme –> affects a single step in metabolic pathway.
How was the hypothesis of Beadle and Tatum characterised?
Oversimplification.
How is the reformulation of: ‘one gene-one polypeptide’ characterised?
Too simple to describe the relationship between genes and proteins.
What did Beadle and Tatum’s experiment found?
Mutations in each of the ‘transformational steps’ between precursor and final products n biosynthesis of arginine.
By what was each step in Beadle and Tatum’s experiment undertaken?
By an enzyme encoded by different DNA sections/genes.
By what can enzymes be formed?
Multiple protein subunits.
What can enzymes include?
Non-protein factors.
What do non-protein factors include?
RNA.
What can genes produce when they are processed in different ways?
Similar, different proteins.
Of what are eukaryote genes composed?
Exons.
Introns.
What do exons code for?
Polypeptide sections.
What do polypeptide sections make up?
The whole protein.
When does splicing occur?
After transcription.
Before translation.
What do differences in splicing alter?
Set of exons.
What do exons produce once they are translated?
The final protein.
What do variations in splicing effect?
Protein structure.
Protein function.
Where can modification of key translational controls like start and stop codons result for proteins?
Missing normal N-terminal.
Longer C-terminals.
What is the N-terminal of a protein?
Front section.
What are C-terminals of a protein?
End sections.
For which organism was in vitro transcription first demonstrated?
Escherichia coli RNA Polymerase.
Who did first demonstrate in vitro transcription for E. coli?
Sam Weiss.
Jerard Hurwitz.
Where could RNA Polymerase be visualised?
On DNA.
How could producing ‘tails’ of RNA by electron microscopy and transcription be followed?
By using 32P. NTPs.
A, C, G, U.
Of how many steps does transcription consist?
3.
What are the 3 stages of transcription?
- Initiation.
- Elongation.
- Termination.
What did analysis of various E. coli mutations found about the 3 steps of transcription?
Any stage could be interrupted to control gene expression.
Many antibiotics target one/more of stages.
By how many subunits is the Core Enzyme composed?
5.
Which are the 5 subunits the Core Enzyme is composed of?
- 2.
- α.
- β.
- β’ .
- ω.
What is the fifth subunit the Holoenzyme includes?
Sigma: σ.
What is Sigma factor of Holoenzyme?
A very large protein complex.
What does RNAP synthesise?
mRNA.
rRNA.
tRNA.
For which activity is the Core enzyme required?
The polymerization.
For what is σ factor required?
Correct initiation of transcription.
What does σ target in transcription?
Upstream region of a gene = operator.
-35 and -10 sites.
What do bacteria have to regulate different gene groups?
Different Sigma factors.
How is the fact that bacteria have f=different genes to regulate different gene groups characterised?
One of the highest-order means of regulating gene expression in bacteria.
By what is transcription controlled?
Non-coding DNA sequences.
Of what do genes consist?
Central ‘coding’ sequence.
To what is the central ‘coding’ sequence translated?
The sequence of amino acids.
An up-stream promoter region.
Down-stream terminator region.
What do amino acids make?
The protein.
What do the up-stream promoter region and the down-stream terminator region control?
Gene expression.
What is the difference between eukaryote gene structure and prokaryote genes?
Eukaryote is more complex.
What is the similarity between eukaryote gene structure and prokaryote genes?
Coding.
Non-coding sections.
When does initiation of transcription begin?
When RNAP binds promoter region of double-stranded DNA.
What happens in transcription?
Two strands melt apart.
Base-pairing first nucleotide to coding strand.
How do transcription and translation occur in prokaryotes?
Tightly coupled.
How do ribosomes exist in prokaryotes?
Lining up along nascent mRNA.
What do ribosomes produce in prokaryotes?
Proteins.
What does RNAP produce when going along DNA?
mRNA.
What did tight coupling of transcription and translation in prokaryotes meant?
In vitro transcription-translation was possible with 3H production.
14C labelled proteins allow protein functions to be investigated. (could not in cells/with cell lyses.
What does eukaryotic mRNA undergo?
Modifications.
Where does eukaryotic mRNA undergo modifications?
In nucleus.
When does eukaryotic mRNA undergo modifications?
Before being exported and translated.
What are some modifications eukaryotic mRNA undergoes?
5’ capping.
3’ poly-A-tailing.
Splicing.
Where do alternative splicing patterns to remove exons and link introns result?
Expression of related proteins.
What do proteins consist of?
Amino acid chains linked together in a specific order.
How is the specific order of linked amino acid chains known?
The primary structure.
From N-terminus to C-terminus.
What can the peptide chain then adopt?
Different structures.
How do different structures of peptide chain occur?
Fold around itself.
How is the final protein formed by different peptides?
When they interact with one another.
How can amino acids be categorised?
By:
Polarity.
Charge.
Size.
How many levels of polypeptide chains folding and interacting with each other exist?
4.
Why do polypeptide chains fold and interact with each other?
To produce the final three-dimensional shape of the mature protein.
What does the genetic code use?
Triplets of DNA bases.
Why does the genetic code use triplets of DNA bases?
To encode the amino acids in a peptide chain.
What is the code of amino acids?
Almost universal.
How many combinations of A, C, G and T ecist?
> 20.
What do some amino acids have?
> 1 triplet.
As what are some triplets used?
Stop signals.
What happens to amino acids in the ribosome?
They are matched to base triplets by tRNAs.
What does the universal code link?
RNA triplets to amino acids.
DNA triplets with amino acids. (more helpful).
What does the expression of reading frame produce?
A protein.
What must the reading frame have?
An appropriate start codon.
An in-frame stop codon.
What is usually the start codon?
AUG.
What are usually the stop codons?
UAA.
UAG.
UGA.
What happens in translation?
Genetic information encoded by DNA, transcribed into mRNA –> converted into amino acid sequences/polypeptides.
By which factor is the template strand of DNA double-stranded helix used?
By RNAP.
What does the template strand of DNA produce when used by RNAP?
mRNA.
What does the amino acid sequence follow?
The coding strand sequence.
What are transfer RNAs?
Short RNA molecules.
Into what structure do tRNAs fold?
‘t’.
‘L’.
Where is the neck of tRNAs linked?
To a specific amino acid.
Where is the bulging foot of tRNA matched?
To the mRNA triplet.
Of what is anticodon composed?
Three bases that interact with mRNA.
Where do ribosomes shuffle?
Along mRNA transcript.
