Genes and proteins: One gene-one protein hypothesis Flashcards
How can one gene be characterised?
As one protein hypothesis.
What are the functions of DNA?
It encodes information in the form of genes.
It is transcribed and translated –> produce functional proteins.
Where are genes linked?
To enzymes/functional proteins.
What is an individual’s genotype?
Their genetic make-up.
What is the phenotype of an individual?
The physical traits.
Characteristics.
By what is the phenotype influenced?
By genotype.
Environment.
How is the G-P map characterised?
Simple.
Direct.
What does the interaction of regulatory systems and pathways form?
Complex networks.
What do the complex networks formed by regulatory systems and pathways interactions, do?
Add additional complexity to G-P maps.
How do genes act?
Through enzymes’ production.
What is each gene responsible for?
Producing a single enzyme.
What does a single enzyme produced by a gene affect?
A step in the metabolic pathway.
Which hypothesis describes the relationship between genes and proteins?
‘one gene - one polypeptide’.
Who formulated the Central Dogma of Molecular Biology?
Francis Crick.
When was the Central Dogma formulated?
In 1957.
What does the Central Dogma of Molecular Biology describe?
The flow of genetic information in a biological system from DNA to proteins.
When was the Central Dogma updated?
In 1970.
What did Crick said about the Central Dogma in 1970?
It deals with detailed residue-by-residue transfer of sequential information. Information cannot be transferred back from protein to protein or nucleic acid.
Why did ‘exceptions’ or ‘adjustments’ were made to the dogma as biology developed?
To facilitate new discoveries.
To better understand systems.
What does the dogma describe after all?
How information flows between DNA and RNA for replication.
How DNA via RNA makes produces proteins and gives a phenotype.
How were metabolic changes recognised?
Through mating experiments.
What was recognised in mating experiments responsible for metabolic mutations?
Phenotypes were not following Mendelian inheritance patterns.
What else can be responsible for metabolic mutations?
Enzymes.
Not linked to genetics.
What did Ephrussi and Beadle investigate in mid-1930?
The eye colour pigments of Drosophila melanogaster fruit flies.
How were the ‘genes’ affecting eye colour appeared?
Serially dependent.
What was the result of pigments through transformations?
Normal red eyes.
What did different eye colour gene mutations disrupt?
Transformations at different points in series.
What are the Drosophila eye-colour pigments?
Complex chemicals.
How are Drosophila eye-colour pigments produced?
By a number of different enzymatic reactions.
What do Drosophila eye-colour pigments produce when combined?
Hues = αποχρώσεις.
What was each gene responsible for?
For an enzyme acting in metabolic pathway of pigment synthesis.
How did they study the metabolic pathways of eye-pigment?
By isolating pigments from the eyes of flies.
Which organism made genetic studies of biochemical traits much easier, as they started isolating fly eye pigments?
Bread mould = Neurospora crassa.
What is the organism Neurospora crassa?
Red bread mould from the phylum Ascomycota.
Eukaryotic.
When was Neurospora crassa organism first isolated?
In 1843.
What are the characteristics of Neurospora crassa organism?
- Grows easy and fast.
- Haploid life cycle –> traits show in offspring.
- Spores in sacks in order –> planted in media.
- Mutated by X-rays when growing on different media.
How can the sacks of spores in Neurospora crassa be removed?
By using micro-dissectors.
When planted in new media –> grow –> analysis.
What can happen in Mapping experiments of Neurospora?
Different strains –> mated –> produce ascospores/sacks –> dissected out –> transferred to fresh agar plates.
What can be determined from the Neurospora mapping experiments?
Offspring’s phenotype.
What did each offspring had inherited in mapping experiments?
2 different genes.
What can we determine by separating the 2 different genes that inherit offspring?
Offspring’s genetic recombination.
What is the aim of using Neurospora crassa in Beadle and Tatum’s experiment?
To link biochemistry of arginine biosynthesis to enzymes and genes.
Where can Neurospora grow?
On minimal media without additional nutrients.
What can Neurospora produce?
All compounds needed for growth.
Amino acids.
Arginine.
What were scientists able to do by isolating arginine mutants in Beadle and Tatum’s experiment with Neurospora crassa?
To place enzyme action into biosynthesis pathway –> produce arginine.
What happens in Isolating arginine mutants process?
- Neurospora –> exposed to –> X-rays –> mutations.
- Ascospores –> isolated –> grow up on –> enriched media.
- Strains –> tested on –> minimal media and minimal media + single amino acids.
Where do strains of Neurospora not able to grow on minimal media, grow instead?
On minimal media + arginine.
When did strains grown on media + arginine mutate?
In the arginine biosynthesis pathway.
What happened in Complementing mutants with Neurospora?
Mutants assessed if they can grow on modified minimal media supplemented with arginine intermediates and arginine in biosynthesis pathway.
What happened to Neurospora mutants when arginine intermediates and arginine in biosynthesis added?
They could be saved on minimal media.
How many enzymes did Neurospora crassa use to produce arginine?
3.
How did Neurospora crassa used 3 agents to produce arginine?
One after the other.
What did Biochemists do during Neurospora crassa using enzymes?
They isolated the enzymes.
Why did Biochemists isolate the enzymes that Neurospora was using?
To convert enzymes into products.
In what was ornithine converted when enzymes were placed in the appropriate order?
To arginine.
What did the mapping experiments with arginine mutants demonstrate?
Arginine mutants were coded by different genome parts/loci.
How are loci recognised?
Genes.
What hypothesis was developed further as molecular biology developed?
One gene - one protein/polypeptide - MULTIPLE POLYPEPTIDES.
By how many proteins can enzymes be formed?
By multiple protein subunits.
What else except protein subunits can enzymes include?
Non-protein factors.
RNA.
What can genes produce once transcribed and translated?
Similar, different proteins.
What shape do proteins/enzymes need to adopt?
A very precise 3-dimensional shape.
Why do proteins need to have a 3-dimensional shape?
To interact with co-factors and substrates.
What can structure changes affect in proteins?
Function.
Lose/generate new functions.
What can the adding of functional domains to an enzyme change?
Functionality.
Of what are eukaryote genes composed?
Exons and introns.
Which part of eukaryote genes composition code for polypeptide to make a whole protein?
Exons.
When do differences in splicing of genes occur?
After transcription.
Before translation.
What do differences in splicing of genes alter?
Exons set.
How are exons involved in protein production?
They are translated.
What do variations in splicing affect in a protein?
Structure.
Function.
Which are the key transitional controls in genes?
Start and stop codons.
In what can modifications of key translational controls result in proteins?
Missing normal N-terminal = front section.
Longer C-terminals = end section.
