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4.7: Translation of RNA to Protein

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RNA to proteins. How?

You must translate. To go from one language to another. Spanish to English, French to German, or nucleotides to amino acids. Which type is the translation of molecular biology? Obviously, the type of translating discussed here translates from the language of nucleotides to the language of amino acids.

Translation

Translation is the second part of the central dogma of molecular biology: RNA → Protein . It is the process in which the genetic code in mRNA is read, one codon at a time, to make a protein. Figure below shows how this happens. After mRNA leaves the nucleus, it moves to a ribosome , which consists of rRNA and proteins. The ribosome reads the sequence of codons in mRNA. Molecules of tRNA bring amino acids to the ribosome in the correct sequence.

Translation. Translation of the codons in mRNA to a chain of amino acids occurs at a ribosome. Find the different types of RNA in the diagram. What are their roles in translation?

To understand the role of tRNA, you need to know more about its structure. Each tRNA molecule has an anticodon for the amino acid it carries. An anticodon is a sequence of 3 bases, and is complementary to the codon for an amino acid. For example, the amino acid lysine has the codon AAG, so the anticodon is UUC. Therefore, lysine would be carried by a tRNA molecule with the anticodon UUC. Wherever the codon AAG appears in mRNA, a UUC anticodon on a tRNA temporarily binds to the codon. While bound to the mRNA, the tRNA gives up its amino acid. Bonds form between adjacent amino acids as they are brought one by one to the ribosome, forming a polypeptide chain. The chain of amino acids keeps growing until a stop codon is reached. To see how this happens, go the link below. http://www.youtube.com/watch?v=B6O6uRb1D38&feature=related (1:29)

The tRNA structure is a very important aspect in its role. Though the molecule folds into a 3-leaf clover structure, notice the anticodon in the lower segment of the molecule (shown in red [left]), with the amino acid attached at the opposite end of the molecule (shown in yellow [right]).

After a polypeptide chain is synthesized, it may undergo additional processes. For example, it may assume a folded shape due to interactions among its amino acids. It may also bind with other polypeptides or with different types of molecules, such as lipids or carbohydrates. Many proteins travel to the Golgi apparatus to be modified for the specific job they will do. You can see how this occurs by watching the animation at this link: http://vcell.ndsu.edu/animations/proteinmodification/movie-flash.htm .

Summary

  • Translation is the RNA → Protein part of the central dogma.
  • Translation occurs at a ribosome.
  • During translation, a protein is synthesized using the codons in mRNA as a guide.
  • All three types of RNA play a role in translation.

Making Connections

Practice I

Use this resource to answer the questions that follow.

  1. Translation needs what three components?
  2. Describe the structure of a ribosome.
  3. Describe the structure and role of a tRNA molecule.
  4. Define codon and anticodon.
  5. How does termination occur?

Practice II

Review

1. Outline the steps of translation.

2. Discuss the structure of a tRNA molecule, and its role in translation.

3. How are transcription and translation related to the central dogma of molecular biology?

Vocabulary

anticodon

anticodon

Sequence of 3 bases in the tRNA molecule at the site where the tRNA and mRNA bind; complementary to the codon in the mRNA.
mRNA

mRNA

(messenger RNA): Type of RNA that copies genetic instructions from DNA in the nucleus and carries them to the cytoplasm.
polypeptide

polypeptide

Chain of amino acids that alone or with other such chains makes up a protein.
ribosome

ribosome

Organelle inside all cells where proteins are made; site of protein synthesis.
rRNA

rRNA

(ribosomal RNA): Type of RNA that helps form ribosomes and assemble proteins.
translation

translation

Process in which genetic instructions in mRNA are read to synthesize a protein.
tRNA

tRNA

(transfer RNA): Type of RNA that brings amino acids to ribosomes where they are joined together to form proteins.

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Difficulty Level:

At Grade

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Date Created:

Feb 24, 2012

Last Modified:

Sep 15, 2014
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