Powerpoint Presentation: The Gene
Molecular Genetics Index
The Chemical Nature if the Gene
The Nucleic Acids
Ribonucleic Acid (RNA)
The Characteristics of the Genetic Code
The Genetic Code
The lac Operon
Topic Chapters Index
are needed by this mould to synthesise vitamins and
The production of these compounds is affected by
The inheritance pattern of these defective enzymes is
the same as that of single genes.
Therefore ONE GENE corresponds to ONE ENZYME
Enzymes are proteins, but not all proteins are enzymes.
They are all affected by mutations in the same way
Therefore ONE GENE corresponds to ONE PROTEIN
proteins are made of subunits each of which is
independently affected by mutations (eg haemoglobin has
2 alpha subunits and 2 beta subunits).
Therefore ONE GENE corresponds to ONE POLYPEPTIDE
Beedle and Tatum (1940) Experiments using the red bread mould Neurospora crassa.
This mould has the advantage of being a haploid individual so all the genes are expressed. Different individuals
can be separated because the spores form in long thin
"pods" called sacs.
Its requirements are simple.
It grows quickly and produces results in a few days.
Producing mutant strains
Alter the genes by mutation and you will alter the dietary requirements
Cross breeding strains
If four of the daughter spores give rise to colonies that are like the deficient parent and four give colonies that are
like the wild type parent:
This is the pattern that Beedle and Tatum found.
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