Beadle and Tatum:
Why was Neurospora a suitable choice as an experimental organism?
It is easy to obtain and use in a laboratory, mutants are easily obtained by X-ray or UV radiation, new generations can be produced in relatively short time frames, having a haploid genome means any mutation appears in the phenotype and it is easy to control variables for growth, e.g. temperature, food supplies etc.
Distinguish between minimal medium and complete medium.
Minimal medium is the basic food supply that is needed to support the wild-type mould. Complete medium has all nutrients added.
How did Beadle and Tatum produce mutant varieties of Neurospora?
Beadle and Tatum exposed it to X-rays and UV radiation to produce mutant varieties.
Beadle and Tatum grew hundreds of different spores. Why did they need to grow so many?
Beadle and Tatum needed to grow hundreds of different spores to obtain the mutants and to repeat experiments for reliability.
Outline the evidence used by Beadle and Tatum to support their hypothesis.
To support their hypothesis Beadle and Tatum showed that some of the mutants forms of Neurospora could not live without a particular amino acid or vitamin added to their food source. These mutants were shown to be missing one particular enzyme which led to a blocked metabolic pathway. They showed that the mutation of a particular gene precented the production of a particular enzyme- the one gene-one enzyme hypothesis.
Explain why the one gene-one protein hypothesis was modified to one gene-one polypeptide.
It was shown that some proteins consisted of several different polypeptide chains and each different polypeptide chain has its own gene, e.g. haemoglobin has two different polypeptide chains. Thus the one gene-one protein hypothesis became the one gene-one polypeptide hypothesis.