Lesson 3 — Protein Synthesis


More Help Reading the mRNA Table

The following diagram is a version of the chart that you receive with the Diploma Examination. It is located in your textbook on page 637. Be sure you have printed a copy of the Biology 30 Data Booklet from the introductory section of the course.




Learn to Read It

Codons are three letters representing bases. The first base is along the left side, the second is along the top, and the last is on the right side.

Example

The mRNA sequence is AUGACGGAGGGGUAUUCUUAA. Determine the amino acid sequence.


Solution

To translate this base sequence into an amino acid sequence, first separate the sequence into three nucleotide codons as shown: 

AUG  ACG  GAG  GGG  UAU  UCU  UAA

The first codon, AUG, codes for methionine (also called the initiator, which begins the process). The second codon, ACG, codes for the amino acid threonine. The third codon, GAG, codes for the amino acid glutamate.

The amino acid sequence is methionine - threonine - glutamate - glycine - tyrosine - serine - stop.



Practice Questions

  1. Use the mRNA codon table to find the amino acid that corresponds to each of the following codons:

    1. GGG
    2. UCU
    3. AGU

  2. What is one RNA codon that corresponds to a "stop" signal?

  3. How many codons correspond to the amino acid leucine?


  1.  
    1. glycine
    2. serine
    3. serine

  2. UAA or UAG or UGA

  3. 6 codons