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Do both strands of DNA contain genes?

  1. Jun 19, 2015 #1
    We know that the gene is part of DNA molecule in organism. I would like to know - are the both strands of DNA equally loaded/”filled” with genes? Or maybe only one strand contains genes? If both strands contain genes then can one gene on one strand “overlap” the other gene on the other strand? On the picture below we see that the Gene 3 on the lower strand partly overlaps the Gene 2 on the upper strand, does this happen?
    D2eojTw.png
     
  2. jcsd
  3. Jun 19, 2015 #2

    jedishrfu

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  4. Jun 19, 2015 #3

    Ygggdrasil

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    This is incorrect. Both strands of DNA can encode genes (though the coding sequence of one gene will always be on one strand). Anti-codons refer to segments of tRNA molecules, not parts of a gene.

    Transcription will often occur from both strands of the DNA at a particular locus producing a sense transcript and an anti-sense transcript. http://www.nature.com/nrg/journal/v14/n12/full/nrg3594.html used to be thought of as an unwanted byproduct of gene regulation, though there are a growing number of examples where the antisense transcripts have functions as long non-coding RNAs (see for example, the Xist and Tsix transcripts involved in X-chromosome inactivation). I am not aware of any examples where a coding sequences on the Watson strand overlaps with a coding sequence on the Crick strand, though there may be some strange DNA viruses where this is the case. There are certainly examples of genes that can encode multiple genes on the same strand of DNA in different reading frames (see for example, the programmed frameshifting that occurs in the gag-pol gene of HIV).
     
    Last edited by a moderator: May 7, 2017
  5. Jun 20, 2015 #4
    Thanks

    Yes of course

    Well, it is a first time I encountered these names :cool:

    It would be interesting to clarify this problem :smile:
     
  6. Jun 20, 2015 #5
    Excuse me, but I do not quite understand what it means. Imagine that we have got DNA and there are two genes located on different strands exactly in front of each other and transcription occurs and we have two RNAs. Do you mean that transcription of one (let’s say upper) will be called sense transcript(ion) and the second one will be called anti-sense transcript(ion)?
    v9KWf2B.png
     
  7. Jun 20, 2015 #6

    Ygggdrasil

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    Yes, if the sense transcript comes from the top strand, it will have the sequence CGUGCGUCUG. The antisense transcript would be transcribed from the bottom strand, and be complementary to the sense transcript (CAGACGCACG). The process of making this complementary RNA molecule is called antisense transcription while the molecule itself is referred to as the antisense transcript. Note that the antisense and sense transcripts arise from transcription at distinct promoters.

    Although antisense transcripts have some region that is complementary to their corresponding sense transcript, they do not always fully overlap the sense transcript and can have regions that do not overlap with the sense transcript. For example, consider this figure from the http://dx.doi.org/10.1038/nrg3594 [Broken] article I linked to earlier:
    nrg3594-f3.jpg
    Here the sense (protein-coding) transcript is shown in blue and the antisense transcript is shown in red. In case (a), the AS transcript partially overlaps with the 5' end of the sense mRNA but the AS transcript also contains regions that do not overlap with the sense transcript. In contrast, in case (d), the sense and antisense transcripts almost fully overlap and thus the two molecules would be reverse complements and bind very strongly via base pairing.
     
    Last edited by a moderator: May 7, 2017
  8. Jun 20, 2015 #7

    jedishrfu

    Staff: Mentor

    Yggg, Nice diagrams -- Jedi
     
  9. Jun 21, 2015 #8
    O, do you mean that the two mRNAs that are produced during transcription AT THE SAME TIME can actually make “double helix” of mRNA or something like that?
     
  10. Jun 21, 2015 #9

    Ygggdrasil

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    They are unlikely to be produced at the same time because the RNA polymerases producing the sense and antisense transcripts would collide and interfere with each other during transcription. However, when the antisense transcript is made, it can bind to already existing sense transcripts to form a double-stranded RNA. Similarly already existing antisense transcripts could bind to newly made sense transcripts.
     
  11. Jun 21, 2015 #10
    Afaik ...
    A gene is a set of bases in one strand of the DNA which encodes the information necessary to construct a useful protein.
    The opposite DNA strand is it's exact complement in terms of encoding but does not construct anything useful
    It serves the purpose only of replicating it's complimentary and active gene, ( which is necessary for replication).
    However the active protein-build instucting gene can be on either side of the DNA chain.
    Am I somewhere near right?
     
  12. Jun 22, 2015 #11

    Ygggdrasil

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    Examples apparently do exist where two protein-coding genes transcribed on opposite stands of the DNA overlap. Here are two papers describing examples in bacteria (http://nar.oxfordjournals.org/content/27/8/1847.full) and mammals (http://www.biomedcentral.com/1471-2164/9/169).
     
  13. Jun 23, 2015 #12
    Thanks, I wanted to know exactly this :cool:

    So, the conclusion is that the genetic sequence on one strand partly determines the genetic information on the other strand. In other words, organism’s traits are somehow interconnected. If one trait changes, then the second trait will also change if these two genes are overlapped, at least partly.
     
  14. Jun 23, 2015 #13

    Ygggdrasil

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    Sure, but genes do not need to be overlapping for traits to be interconnected. That one trait can influence the expression of another trait encoded by a different gene is a phenomenon known as epistasis and is quite common in genetics (as opposed to overlapping genes which are relatively rare).
     
  15. Jun 24, 2015 #14
  16. Mar 9, 2016 #15
    Do both DNA strands contain coding genes???? please reply me fast
     
  17. Mar 9, 2016 #16
    The gene, (a sequence of bases called nucleotides), which codes for the production of any particular protein is on one strand, while the opposite strand serves as a template for DNA replication.
    However the active protein generating sequence isn't always in the same strand for every protein.
    There are some rare cases where both strands contain active protein coding instructions at the same site within the DNA.
    DNA provides the 'blueprints' from which other cellular apparatus constructs proteins.
    These proteins, slightly different for different individuals, are then used by the organism for it's physical growth, (making new cells) as well as many other things.
    http://www.uvm.edu/~cgep/Education/Gene2Prot.html [Broken]
    http://genetics.thetech.org/about-genetics/how-do-genes-work
     
    Last edited by a moderator: May 7, 2017
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