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Question about Genetic Code

  1. May 11, 2005 #1
    I'm having problems with three terms that are used to describe the genetic code:
    non-overlapping reading frame

    1) Universality: For the most part, I understand. I know that the universality of the code allows for the limited exchange of genetic information among different types of organisms, and the activities of molecules such as viruses. However, I still don't get what "Universality" really is. Is it the fact that all life comes from one source?

    2) Redundancy: all but two of the twenty amino acids (methionine and tryptophan) can be specified by more than one codon. Is this the only definiton of redundancy?

    Thank you
  2. jcsd
  3. May 11, 2005 #2


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    Universality is the fact that codons have the same meaning (with a few exceptions) in virtually all species. The universality of the genetic code can be used to imply that the three domain of life shared a common evolutionnary developments. It also implies that genetic information can be transfer from one organism to another as you stated.

    As far as the genetic code is concern, it is the only function. In broad sense in biology, more specifically genetics, redundancy can also be used in the context of gene and their functions. Sometimes genes will duplicate and therefore the newly created gene will have reduntant function. Also, 2 gene, which have a seperated origin, may have the same function.

    A open reading frame (ORF) is a strech of codons, with a start and stop codon, that has the potential to encode a complete protein. Non-overlapping reading frame is basicly 2 ORF that are speparated by 1 or more nucleotides.
  4. May 13, 2005 #3
    An example of the ORF would be:

    Imagine a good ORF that codes for a functional gene

    e.g. THE BIG FAT CAT ATE RAT We can call this ORF 1 where each word is a codon

    If we shift this ORF by just one nucleotide,

    e.g. HEB IGF ATC ATA TER AT... The whole sequence does not make sense anymore, and will code for a nonfunctional or different gene.

    So when we say that the genetic code has a non-overlapping reading frame... it means that codons must be read in one specific way (e.g. ORF 1). If read in a different way, the intended gene will not be translated into the correct protein.

    The genetic code having redundancy basically means that there's always a backup plan. Also, there are different combinations of three nucleotides (codons) that can code for the same amino acid, giving extra redundancy to the genetic code.

    Hope this helps a bit
  5. May 19, 2005 #4
    One interesting thing about the genetic code is that eukaryotes generally have mitochondria (basically an aerobic energy producing organelle). The mitochondria have DNA that has a different genetic code then the chromosomal DNA. This may suggest that mitochondria once were single cell organisms that had a different genetic code the prokaryotic ancesters.
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