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  • The DNA double helix contains two linear sequences of

  • the letters A C G and T, which carry coded instructions.

  • Transcription of DNA begins with a bundle of factors

  • assembling at the start of a gene, to read off the information

  • that will be needed to make a protein.

  • The blue molecule is unzipping the double helix and

  • copying one of the two strands.

  • The yellow chain snaking out of the top

  • is a close chemical cousin of DNA called RNA.

  • The building blocks to make the RNA enter through an intake hole.

  • They are matched to the DNA - letter by letter - to copy the gene.

  • At this point the RNA needs to be edited before

  • it can be translated into a protein.

  • This editing process is called splicing, which involves removing

  • the green non-coding regions called "introns",

  • leaving only the yellow, protein-coding "exons."

  • Splicing begins with assembly of factors at the intron/exon borders,

  • which act as beacons to guide small proteins to form

  • a splicing machine, called the spliceosome.

  • The animation is showing this happening in real time.

  • The spliceosome then brings the exons on either side of

  • the intron very close together, ready to be cut.

  • One end of the intron is cut and

  • folded back on itself to join and form a loop.

  • The spliceosome then cuts the RNA to release the loop and

  • join the two exons together.

  • The edited RNA and intron are released,

  • and the spliceosome disassembles.

  • This process is repeated for every intron in the RNA.

  • Numerous spliceosomes remove all the introns

  • so that the edited RNA contains only exons,

  • which are the complete instructions for the protein.

  • Again, this is happening in real time.

  • When the RNA copy is complete,

  • it snakes out into the outer part of the cell.

  • Then all the components of a molecular factory called a ribosome

  • lock together around the RNA.

  • It translates the genetic information in the RNA into

  • a string of amino acids that will become a protein.

  • Special transfer molecules - the green triangles -

  • bring each amino acid to the ribosome.

  • Inside the ribosome, the RNA is pulled through like a tape.

  • There are different transfer molecules for each of

  • the twenty amino acids, shown as small red tips.

  • The code for each amino acid is read off the RNA,

  • three letters at a time,

  • and matched to three corresponding letters on the transfer molecules.

  • The amino acid is added to the growing protein chain and after

  • a few seconds the protein starts to emerge from the ribosome.

  • Ribosomes can make many proteins.

  • It just depends what genetic message you feed into the RNA.

The DNA double helix contains two linear sequences of

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B2 US rna protein amino ribosome amino acid dna

The Central Dogma of Biology

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    Szu-Pei Wu posted on 2018/10/29
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