central dogma of molecular biology


  • The effective information content has been changed by means of the actions of a protein or proteins on DNA, but the primary DNA sequence is not altered.

  • The unknown transfers describe: proteins being synthesised directly from a DNA template without the use of mRNA, a protein being copied from a protein, synthesis of RNA using
    the primary structure of a protein as a template, DNA synthesis using the primary structure of a protein as a template – these are not thought to naturally occur.

  • This is an example of protein directly editing DNA sequence, as well as increasing the sequence’s heritable propagation.

  • Special transfers of biological sequential information Reverse transcription[edit] Unusual flows of information highlighted in green Main article: Reverse transcription Reverse
    transcription is the transfer of information from RNA to DNA (the reverse of normal transcription).

  • Transcription[edit] Main article: Transcription (genetics) Transcription is the process by which the information contained in a section of DNA is replicated in the form of
    a newly assembled piece of messenger RNA (mRNA).

  • This process causes the intein sequence to be copied from the original source gene to the intein-free gene.

  • In prokaryotic cells, which have no nuclear compartment, the processes of transcription and translation may be linked together without clear separation.

  • It is the process by which genetic information from RNA gets transcribed into new DNA.

  • The transfers of information described by the central dogma ideally are faithful, deterministic transfers, wherein one biopolymer’s sequence is used as a template for the
    construction of another biopolymer with a sequence that is entirely dependent on the original biopolymer’s sequence.

  • [12] RNA editing, in which an RNA sequence is altered by a complex of proteins and a “guide RNA”, could also be seen as an RNA-to-RNA transfer.

  • [10] General transfers of biological sequential information DNA replications[edit] Main articles: DNA replication and Replisome In the sense that DNA replication must occur
    if genetic material is to be provided for the progeny of any cell, whether somatic or reproductive, the copying from DNA to DNA arguably is the fundamental step in information transfer.

  • It states that such information cannot be transferred back from protein to either protein or nucleic acid.

  • Although this is a form of protein affecting protein sequence, not explicitly covered by the central dogma, there are not many clear examples where the associated concepts
    of the two fields have much to do with each other.

  • This is a case of a protein changing its own primary sequence from the sequence originally encoded by the DNA of a gene.

  • The replisome comprises:[11] • A helicase that unwinds the superhelix as well as the double-stranded DNA helix to create a replication fork • SSB protein that binds open the
    double-stranded DNA to prevent it from reassociating • Primase adds a complementary RNA primer to each template strand as a starting point for replication • DNA polymerase III that reads the existing template chain from its 3′ end to its 5′
    end and adds new complementary nucleotides from the 5′ end to the 3′ end of the daughter chain • DNA polymerase I that removes the RNA primers and replaces them with DNA • DNA ligase that joins the two Okazaki fragments with phosphodiester
    bonds to produce a continuous chain This process typically takes place during S phase of the cell cycle.

  • A complex group of proteins called the replisome performs the replication of the information from the parent strand to the complementary daughter strand.

  • The general transfers describe the normal flow of biological information: DNA can be copied to DNA (DNA replication), DNA information can be copied into mRNA (transcription),
    and proteins can be synthesized using the information in mRNA as a template (translation).

  • The encoding of proteins is done in groups of three, known as codons.

  • Direct translation from DNA to protein[edit] Direct translation from DNA to protein has been demonstrated in a cell-free system (i.e.

  • In turn it can convey information into new cells and reconfigure more functional molecules of that sequence into the alternate prion form.

  • Some proteins then excise internal segments from their own peptide chains, splicing the free ends that border the gap; in such processes the inside “discarded” sections are
    called inteins.

  • Rather, it claims that there is a source of information within protein molecules that contributes to their biological function, and that this information can be passed on
    to other molecules.

  • Other proteins must be split into multiple sections without splicing.

  • It is often stated as “DNA makes RNA, and RNA makes protein”,[1] although this is not its original meaning.

  • In some types of prion in fungi this change is continuous and direct; the information flow is Protein → Protein.

  • In eukaryotic cells, the site of transcription (the cell nucleus) is usually separated from the site of translation (the cytoplasm), so the mRNA must be transported out of
    the nucleus into the cytoplasm, where it can be bound by ribosomes.

  • The enzymes that copy RNA to new RNA, called RNA-dependent RNA polymerases, are also found in many eukaryotes where they are involved in RNA silencing.

  • Methylation[edit] Main article: Epigenetics Variation in methylation states of DNA can alter gene expression levels significantly.

  • I had already used the obvious word hypothesis in the sequence hypothesis, and in addition I wanted to suggest that this new assumption was more central and more powerful.

  • The family of enzymes involved in this process is called Reverse Transcriptase.

  • However, it was unclear whether this mechanism of translation corresponded specifically to the genetic code.

  • [2] The dogma is a framework for understanding the transfer of sequence information between information-carrying biopolymers, in the most common or general case, in living


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book}}: |work= ignored (help)

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