Genetic Code - Features and Codons - Unsolved Practice Set
Chapter: Molecular Basis of Inheritance | Topic: Genetic Code Features and Codons
GENETIC CODE - FEATURES AND CODONS - UNSOLVED PRACTICE SET
Topic: Genetic Code Features and Codons
Multiple Choice Questions
Q1. The genetic code is described as a triplet code because:
- Each amino acid is coded by a single nucleotide
- Each amino acid is coded by a sequence of three nucleotides (a codon)
- Each amino acid requires four nucleotides
- Codons overlap with each other
Q2. The total number of possible codons formed from the four nitrogenous bases, taken three at a time, is:
- 4
- 16
- 64
- 20
Q3. The start codon that also codes for the amino acid methionine is:
- UAA
- UAG
- AUG
- UGA
Q4. The genetic code is said to be "degenerate" because:
- Some amino acids are coded by more than one codon
- Some codons code for no amino acid at all
- Every amino acid has exactly one codon
- The code varies randomly between organisms
Q5. Which of the following is NOT a stop (termination) codon?
- UAA
- UAG
- UGA
- AUG
Short Answer Questions
Q6. What is meant by the genetic code being described as a "triplet code"?
Q7. Why is the genetic code considered "nearly universal"? Mention one minor exception if you know of any.
Q8. What is meant by the "degeneracy" of the genetic code? Give one example.
Q9. Name the start codon and the three stop codons of the genetic code.
Long Answer Questions
Q10. Discuss the important features of the genetic code, including its triplet nature, degeneracy, and universality.
Q11. Explain the significance of Nirenberg's experiments in helping scientists decipher the genetic code.
APPLICATION / ANALYSIS
Q12. A student calculates that with 4 nitrogenous bases and a triplet code, 64 codons are possible, but only 20 amino acids exist in proteins. Explain, using the concept of degeneracy, how this "extra" number of codons is accounted for.
Q13. A mutation changes a single base in a codon such that it now reads as one of the stop codons (UAA, UAG, or UGA) instead of an amino acid-coding codon. Predict what effect this mutation would have on the protein being synthesised, and explain your reasoning.