It is very difficult to study the actions of essential genes in organisms, especially haploid
organisms such as
, due to the often result of death from mutations of
Conditional mutations, such as temperature sensitive mutations, are a very
useful tool in studying these genes, and they can be turned on and off by a change of
We investigated temperature sensitivity mutations in
the structure of said mutations compared to wild type
We selected for mutants on
FOA selective media, then moved mutants to uracil dropout plates, set in three different
Any mutants found to grow on both FOA and low temperature
uracil dropout could possibly be a ts mutant we were looking for.
We found a
specimen containing an A107P mutation in Ura3p, pluss two silent mutations also within the
This specimen grew on FOA, but failed to grow on uracil dropout at any
The mutation A107P in
does not lead to a temperature sensitive Ura3p
protein, but leads to a complete loss of function protein.
Further studies will assess the reason
A107P causes a complete loss of function and not a temperature sensitive
Genes are sequences of DNA that code for the production for specific proteins.
three nucleotide bases of DNA codes for the incorporation of a specific amino acids into the
protein primary structure.
This means that mutations, or changes, in the DNA sequence may
lead to the incorporation of new amino acids into the protein, which changes its structure, and
thereby changes its functionality.
These mutant proteins can be totally ruined, and lose
function, be mostly unaffected, and retain functionality, or be altered just enough to function
under certain conditions, while becoming nonfunctional under other conditions.
These types of
mutations lead to what is called a conditional mutant organism, one which appears wild type in
one setting, but may appear mutant in another.
We screened a culture of
) to identify and
characterize a type of conditional mutation called a temperature sensitive (TS) mutation.
mutation is one that causes a protein to be functional under normal temperatures, (30
C for our
), but dysfunctional at a higher temperature (37
C).(Pizzagalli et al 1988)
specifically we were searching for a TS mutation of orotidine-5’phosphate decarboxylase
(ura3p), an enzyme which functions in the production of uracil.
Since Ura3p functions in the
production of uracil, and uracil is needed for RNA production, the prevalence of mutations in