Tatum & Beadle Qu.

[jnney]

Hi guys,

I'm a bit confused about this dot point.

Here is some information I obtained from the Biology in Focus textbook:

1. They irradiated the bread mould Neurospora crassa with X-rays to induce mutations. The resulting mould forms they called mutants.
2. Further experimentation showed that some of the mutants could no longer produce an essential amino acid (implying that a particular enzyme was no longer functioning).

- and the Heinemann textbook:

They used X-rays to produce millions of mutated strains of the mould. Each strain lacked the ability to produce one of the essential nutrients (an amino acid or a vitamin) that would be needed to grow normally. This inability was caused by the absence of the necessary enzyme.

Does this mean that enzymes make amino acids? Or I have I completely missed the point?

[madharris]

I haven't done this dot point yet so I might be wrong
But I thought enzymes were proteins made up of long amino acid chains, joined together by peptide bonds to form polypeptide chains?.... (from dotpoint 1 of MAB)

so maybe you've missed the point?

[jnney]

That's what I thought too.

[sidaoui]

beadle and tatum found that if the minimal medium was supplemented with a particular amino acid, the mutant strand of neurospora would grow.
this suggested that the mutant had lost the ability to produce a particular amino acid because they lacked particular enzymes.
e.g. a mutant strand that required alanine to grow lacked the enzyme to produce alanine.

[jnney]

I emailed my teacher and this is her response. Hopefully this will be of help to other students.

Enzymes are proteins. A gene mutation prevents a specific polypeptide being produced which then prevents the enzyme from being produced. Enzymes catalyse reactions, including the reactions which produce amino acids. The reaction by which the amino acid arginine is produced has a number of steps, each involving a different enzyme. Neurospora requires arginine to grow and if any of the enzymes are missing it will not grow. Thus, enzymes do not make amino acids, they catalyse the reaction.

[Kimyia]

I emailed my teacher and this is her response. Hopefully this will be of help to other students.

Enzymes are proteins. A gene mutation prevents a specific polypeptide being produced which then prevents the enzyme from being produced. Enzymes catalyse reactions, including the reactions which produce amino acids. The reaction by which the amino acid arginine is produced has a number of steps, each involving a different enzyme. Neurospora requires arginine to grow and if any of the enzymes are missing it will not grow. Thus, enzymes do not make amino acids, they catalyse the reaction.

Thanks! That makes a lot of sense.
Your teacher sounds brilliant.

[jnney]

Hehe.

[Coookies]

I emailed my teacher and this is her response. Hopefully this will be of help to other students.

Enzymes are proteins. A gene mutation prevents a specific polypeptide being produced which then prevents the enzyme from being produced. Enzymes catalyse reactions, including the reactions which produce amino acids. The reaction by which the amino acid arginine is produced has a number of steps, each involving a different enzyme. Neurospora requires arginine to grow and if any of the enzymes are missing it will not grow. Thus, enzymes do not make amino acids, they catalyse the reaction.

But thats not what the dot point asks for...

[jason2kool]

The 'one gene-one protein' hypothesis was changed as many proteins are made up of more than one polypeptide chain, e.g. haemoglobin is made of two different types of chains and each type is controlled by a different gene. Thus it became 'One gene-One polypeptide'.