5 - From Gene to Protein Flashcards
Alkaptonuria
An autosomal recessive trait with altered metabolism of homogentisic acid.
Affected individuals do not produce the enzyme needed to metabolize this acid, and their urine turns black
Archibold Garrod
- Defects in genetic material can lead to specific diseases, which can be inherited.
- Mendelian Genetic inheritance can be observed in humans.
- Lack of an enzyme is due to a defect in a gene.
why were Neurospora used during beadle and Tatum’s experiments?
- genetically simple
- easy system to test for defects in metabolic pathways
Beadle and Tatum experiment
1) Expose bread mould to X-Rays
2) Place bread mould in multiple test tubes with a ‘complete medium’ – Large variety of available amino acids – and monitor mould growth
3) Place bread mould in multiple test tubes with a ‘ incomplete medium’ – Limited amino acid availability – and monitor mould growth
4) Place samples of any moulds that failed to grow in the incomplete medium in a variety of test tubes, each containing a specific amino acid and record which amino acids allowed the mould to grow
Conclusions of the beadle and tatum experiment
-This suggests genes are each responsible for a specific amino acid (protein) each, thus when they mutate they disturb the production of that amino acid/protein, as shown.
One gene - one protein hypothesis
screening for auxotrophic mutants
- culture individual spores on complete medium
- transfer minimal medium to identify possible auxotrophs
- test candidates for growth on MM supplemented with different classes of nutrients
- test candidates for growth on MM supplemented with individual amino acids
- identify the amino acid that allows your mutant to grow
Srb and Horowitz experiment
identified 3 classes of arginine auxotroph
‘one gene - one enzyme’ hypothesis
- Role of a gene is to encode an enzyme - and that for each enzyme there is a gene
one gene-one polypeptide hypothesis
The premise that a gene is a segment of DNA that codes for one polypeptide.
one gene-one polypeptide hypothesis
The premise that a gene is a segment of DNA that codes for one polypeptide.
How do genes specify proteins?
through transcription and translation
RNA structure
a polymer of nucleotides containing ribose sugar and combinations of four bases: adenine, guanine, cytosine and uracil – usually single-stranded
pulse-chase experiment
A type of experiment in which a population of cells or molecules at a particular moment in time is marked by means of a labeled molecule (pulse) and then their fate is followed over time (chase).
Central Dogma of Molecular Biology
transcription translation
DNA ——————–> RNA —————> protein
translation
synthesis of a mRNA molecule using one strand of the DNA as a template such that G pairs with C and A pairs with U
- catalysed by RNA polymerase
