Examples of Codons: Start Codon, Stop Codons, and Amino Acid Codons

📚 Quick Study Guide

• 🧬 A codon is a sequence of three nucleotides (DNA or RNA) that corresponds to a specific amino acid or stop signal during protein synthesis.
• 🚦 The start codon, usually AUG, signals the beginning of translation. It also codes for methionine in eukaryotes and formylmethionine in prokaryotes.
• 🛑 Stop codons (UAA, UAG, UGA) signal the end of translation; they do not code for any amino acid.
• 🧪 Each codon codes for a specific amino acid according to the genetic code, which is degenerate (more than one codon can code for the same amino acid).
• 🧮 The genetic code is nearly universal across all organisms, implying a common evolutionary origin.

Practice Quiz

1. Which of the following codons is most commonly used as the start codon?

   1. AAA
   2. AUG
   3. UAG
   4. GGG

2. Which of the following is a stop codon?

   1. AUG
   2. GUA
   3. UAA
   4. AGC

3. What is the role of a stop codon in protein synthesis?

   1. To initiate translation
   2. To terminate translation
   3. To add an amino acid
   4. To repair DNA

4. If a codon is 'GCA', which amino acid will it code for?

   1. Alanine
   2. Arginine
   3. Aspartic Acid
   4. Glycine

5. Which of the following statements is true regarding the genetic code?

   1. Each codon codes for multiple amino acids.
   2. Multiple codons can code for the same amino acid.
   3. The genetic code varies greatly between species.
   4. Only one start codon exists.

6. Which of the following is NOT a stop codon?

   1. UAG
   2. UAA
   3. UGA
   4. GAU

7. What does it mean for the genetic code to be degenerate?

   1. It is easily mutated.
   2. It is broken or damaged.
   3. Multiple codons can code for the same amino acid.
   4. It only codes for essential amino acids.