Current Level

 Replication
 Transcription
 Translation
 PCR
 DNA synthesis
 DNA sequencing

Previous Level

 BioWeb Home
 
 Seq Anal
 Theory
 Bioinformatics
 Mo Bio Lecture
 
 Translation

Molecules involved in translation

Translation is a process where genetic information is translated from a ``nucleic acid language" to an "amino acid language".  Translation is catalyzed by a large enzyme called a ribosome, which contains proteins and ribosomal RNA (rRNA).  Translation also involves specific RNA molecules called transfer RNA (t-RNA) which can bind to three basepair codons on a messenger RNA (mRNA) and also carry the appropriate amino acid encoded by the codon.  The ribosome assembles on the first AUG (start codon) in the mRNA.  This codon encodes the amino acid methionine (Met). 

 

Open Reading Frame

Once the start codon is identified, each sequential group of three base pairs form the next codon.  In this way the position of the start codon determines the open reading frame, or order of codons that will be read to form the protein.  In the example below, once the ribosome assembles on the first AUG, the order of the rest of the codons is set for the rest of the translation of the mRNA.

 

The Genetic Code

The 1968 Nobel Prize in Medicine was awarded for deciphering the Genetic Code.  The genetic code is used to translate three base codons in RNA or DNA (recall that U=T in RNA and DNA respectively) into amino acids (given in their three letter and one letter codes).  Scientists now use computer programs to translate DNA sequences into predicted amino acid sequences.  Translation stops when a stop codon (UAA, UAG, or UGA) is reached, and a termination factor causes the ribosome to dissociate from the mRNA.

First

Position

 

 

Second

 

Position

 

Third

Position

 

U

C

A

G

 

 

Phe (F)

Ser (S)

Tyr (Y)

Cys (C)

U

U

Phe (F)

Ser (S)

Tyr (Y)

Cys (C)

C

 

Leu (L)

Ser (S)

Stop

Stop

A

 

Leu (L)

Ser (S)

Stop

Trp (W)

G

 

Leu (L)

Pro (P)

His (H)

Arg (R)

U

 

Leu (L)

Pro (P)

His (H)

Arg (R)

C

C

Leu (L)

Pro (P)

Gln (Q)

Arg (R)

A

 

Leu (L)

Pro (P)

Gln (Q)

Arg (R)

G

 

Ile (I)

Thr (T)

Asn (N)

Ser (S)

U

 

Ile (I)

Thr (T)

Asn (N)

Ser (S)

C

A

Ile (I)

Thr (T)

Lys (K)

Arg (R)

A

 

Met (M)

Thr (T)

Lys (K)

Arg (R)

G

 

Val (V)

Ala (A)

Asp (D)

Gly (G)

U

 

Val (V)

Ala (A)

Asp (D)

Gly (G)

C

G

Val (V)

Ala (A)

Glu (E)

Gly (G)

A

 

Val (V)

Ala (A)

Glu (E)

Gly (G)

G

Try matching the following codons to their respecitve amino acids.

 

Steps in Translation

  • The following movie illustrates the translation of a mRNA by a ribosome and tRNAs. Note that the ribosome assembles on the first AUG (start codon) in the mRNA. Once the start codon has been identified, the rest of the codons in the mRNA are read sequentially.  When a stop codon is encountered a termination factor (TF) binds to the mRNA and causes the ribosome to dissociate, releasing the protein.

A Flash animation of translation in a eukaryote.

 

Practice Exercises (putting it all together)

  • In this practice exercise you need to assemble the ribosome and appropriate tRNA at the start codon for translation to begin.  Review the movie above if you need a refresher.

Drag the appropriate subunit of the ribosome and appropriate tRNA to the start codon to begin translation.

 

  • In this practice exercise, the ribosome assembles at the start codon, you need to choose the appropriate anticodon from a table for translation to proceed.  The anticodons are written 3' to 5', and thus are antiparallel to the codons in the mRNA.

Click on the appropriate anticodon for translation to proceed.

 

  • In this final practice exercise you need to both assemble the ribosome at the start codon, and then drag the appropriate tRNA to match each codon for translation to occur.

Drag the appropriate subunit of the ribosome and appropriate tRNA to the start codon to begin translation.  Then drag each sequential tRNA to the appropriate codon for translation to proceed.

  • More interactive activities can be found at the following site on Translation.
uwsa_l5

  2006 The Board of Regents of the University of Wisconsin System.

Click here to email comments to Scott Cooper regarding this site or its links.