I still don't understand why 'one gene - one protein' was changed to 'one gene - one polypeptide'... i know it has something to do with proteins containing more than one polypeptide chain, cause that's what i've read in textbooks... but it still doesn't make sense to me so could someone please explain it to me?! Thanks.
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one gene - one polypeptide (1 Viewer)
- Thread starter whatbetch
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Alright. Heres a thing u should remember. Atoms form amino acids. Amino acids form polypeptides. Polypeptides form Proteins. Basically, Beadle and Tatum thought that every gene (thus, one gene) lead directly to the formation of one protein (thus, one protein). However, (as u learned from protein synthesis processes) you would know that genes lead to the direct formaiton of polypeptides, not proteins. Proteins are indirectly formed, but this is a step later, when polypeptides themselves (produced from genes) are binded together to form protenis. So basically, Beadle and Tatum thought that every gene made one protein, but it was actually found that every gene made one polypeptide instead. Beadle and Tatum wernt completely incorrect, cos these polypeptides (produced from the genes) do eventually form proteins, but they were one step ahead of themselves.
clarebear14
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i needed help with this crappy thing aswell and it finally makes sence.. Thank you
pardon? What r u tryin to say? :-|
ahh hang on i get ya now. Yeah its sayin that if there if a mutation, it will affect what type of polypeptide is produced. This will in turn affect what types of proteins are made. Proteins are essential, and include standard proteins, homones and enzymes. Other self made biomolecules also fall under the bracket of proteins. In the beadle and tatum experiments, they exposed some bread mould to x rays. This caused them to have mutations, and these mutant mould would die unless they were given a nutrient solution by the scientists. This nutrient solution kept them alive, because this replenished them with the proteins that they needed to live. They normal mould not exposed to the x rays didnt need the solution, because they had normal genes, and thus could make their own correct polypeptides (and thus proteins) to keep them alive. The mutants could not live without the solution, because their genes were altered, and therefore the proteins they were making from polypeptide synthesis were altered. Because they were altered, they didnt work properly. Plus, the production of this new (bogus) protein was a replacement for a protein needed for life. Without this protein, they would die (but the didnt die cos of the nutrient solution given to them). I know thats a whole heep of info, but i hope it makes sense.
annikab
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Beadle and Tatum were not wrong in their hypothesis or experiment. They were just essentially lucky that the production of arginine (a nutrient needed for growth) in bread mould is only controlled by one polypeptide, which is in turn controlled by one gene.
Their theory had to be changed however, as this is not applicable to all living organisms. In fact, many genes control the production of one protein (= many polypeptide chains bound together).
Their theory had to be changed however, as this is not applicable to all living organisms. In fact, many genes control the production of one protein (= many polypeptide chains bound together).
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christoffpow
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'Neospora Crassa' was the bread mould they experimented with. Basically they exposed the bread to x-rays to induce mutations in the particular gene sequences, that were required to produce the polypeptide controlling the growth of the mould. Hence, these mutations led to the production of disfunctional polypeptides (enzymes), which led to the inhibitation of bread mould (mould would not grow). Beadle and Tatum discovered the mould would grow, however, when a specific amino acid was added to the bread. This led them to discover the one gene one enzyme theory... that for every enzyme there lies a particular gene sequence. this was later changed to one gene one polypeptide because not all genes code for enzymes, and that genes are not the only form of proteins. Genes also code for structural proteins (the shape of your nose), and hence the theory was later refined to 'one gene-one polypeptide' = structural proteins and enzymes are both polypeptides.
christoffpow
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Yep. they were really lucky with their choice of experiment.
Spark_Coaching
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Beadle and Tatum used bread mould to investigate nutritional mutations. Using X-rays, they produced mould that was unable to produce a specific amino acid. The mould was unable to grow unless the amino acid was added. They showed that genes controlled biochemical processes. Their hypothesis was that for each gene there was one enzyme or protein. The enzymes that they studied consisted of one polypeptide but many enzymes consist of chains of polypeptides. Therefore, the hypothesis has been changed to the “one – gene one – polypeptide” hypothesis.
They already knew that each gene codes for one polypeptide BUT they thought that ONE protein is made up of only ONE polypeptide so thought ah well, might as well name it one gene one protein hypothesis. Later on it was discovered that some proteins, e.g haemoglobin is actually made up of TWO polypeptides and each of those two polypeptide is coded by a different gene so going by their original logic/hypothesis it should be two gene one protein. thus the need to change the hypothesis to one gene one polypeptide arose in order to be more specific.
1 gene = 1 polypeptide is what they thought and still applies today.
Back then they though that proteins are made of ONE polypeptide ONLY.
So they had though 1 gene = 1 polypeptide = 1 protein
So they thought.. long story told short: 1 gene = 1 protein
Now however it is known that proteins can be made up of MORE than one polypeptides e.g haemoglobin which is made of 2 polypeptides.
So using their logic. 2 gene = 2 polypeptide = 1 protein... That however is not correct (look at it from mathematical/equation perspective if ya want).
i.e by their rule (long story told short) 2 gene = 1 protein. Their origianl rule states however that 1 gene = 1 protein tsk tsk tsk contradicting much?
So currently it is known as 1 gene = 1 polypeptide (i.e no need to falsely "long story told short" and no need to skip detail)
capisce?
Back then they though that proteins are made of ONE polypeptide ONLY.
So they had though 1 gene = 1 polypeptide = 1 protein
So they thought.. long story told short: 1 gene = 1 protein
Now however it is known that proteins can be made up of MORE than one polypeptides e.g haemoglobin which is made of 2 polypeptides.
So using their logic. 2 gene = 2 polypeptide = 1 protein... That however is not correct (look at it from mathematical/equation perspective if ya want).
i.e by their rule (long story told short) 2 gene = 1 protein. Their origianl rule states however that 1 gene = 1 protein tsk tsk tsk contradicting much?
So currently it is known as 1 gene = 1 polypeptide (i.e no need to falsely "long story told short" and no need to skip detail)
capisce?
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