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  • The job of this mRNA is to carry the gene's message from the DNA out of

  • the nucleus to a ribosome for production of the particular protein that this gene codes for.

  • There can be several million ribosomes in a typical eukaryotic cell.

  • These complex catalytic machines use the mRNA copy of the genetic

  • information to assemble amino acid building blocks into the

  • three-dimensional proteins that are essential for life.

  • Let's see how it works.

  • The ribosome is composed of one large and one small sub unit that assemble around the messenger RNA,

  • which then passes through the ribosome like a computer tape.

  • The amino acid building blocks, that's the small glowing red molecules,

  • are carried into the ribosome attached to specific transfer RNAs;

  • that's the larger green molecules also referred to as tRNA.

  • The small sub unit of the ribosome positions the mRNA so that it

  • can be read in groups of three letters known as a codon.

  • Each codon on the mRNA matches a corresponding anti-codon on the base

  • of a transfer RNA molecule.

  • The larger sub unit of the ribosome removes each amino acid and joins it onto

  • the growing protein chain.

  • As the mRNA is ratcheted through the ribosome, the mRNA sequence is

  • translated into an amino acid sequence.

  • There are three locations inside the ribosome designated the A-Site, the

  • P-Site, and the E-Site.

  • The addition of each amino acid is a three-step cycle;

  • first the tRNA enters the ribosome at the A-Site, and is tested for

  • a codon / anti-codon match with the mRNA.

  • Next, provided there is a correct match, the tRNA is shifted to the P-Site,

  • and the amino acid carries is added to the end of the amino acid chain.

  • The mRNA is also ratcheted on three nucleotides, or one codon.

  • Thirdly, the spent tRNA is moved to the E-Site, and then ejected from the

  • ribosome to be recycled.

  • As the protein synthesis precedes, the finished chain emerges from the ribosome;

  • it folds up into a precise shape, determined by the exact order of amino acids.

  • Thus the central dogma explains how the four-letter DNA code is, quite literally, turned into flesh and blood.

The job of this mRNA is to carry the gene's message from the DNA out of

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B2 US ribosome mrna amino amino acid acid trna

mRNA Translation (Advanced)

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    Szu-Pei Wu posted on 2018/10/29
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