Table of contents

1. Introduction to Genetics51m
2. Mendel's Laws of Inheritance3h 37m
3. Extensions to Mendelian Inheritance2h 41m
4. Genetic Mapping and Linkage2h 28m
5. Genetics of Bacteria and Viruses1h 21m
6. Chromosomal Variation1h 48m
7. DNA and Chromosome Structure56m
8. DNA Replication1h 10m
9. Mitosis and Meiosis1h 34m
10. Transcription1h 0m
11. Translation58m
12. Gene Regulation in Prokaryotes1h 19m
13. Gene Regulation in Eukaryotes44m
14. Genetic Control of Development44m
15. Genomes and Genomics1h 50m
16. Transposable Elements47m
17. Mutation, Repair, and Recombination1h 6m
18. Molecular Genetic Tools19m
- Genetic Cloning
  9m
- Methods for Analyzing DNA
  9m
19. Cancer Genetics29m
- Overview of Cancer
  21m
- Cancer Mutations
  7m
20. Quantitative Genetics1h 26m
21. Population Genetics50m
- Hardy Weinberg
  19m
- Allelic Frequency Changes
  31m
22. Evolutionary Genetics29m

11. Translation

The Genetic Code

Genetics

11. Translation

The Genetic Code

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1:54 minutes

Problem 13a

Textbook Question

Third-base wobble allows some tRNAs to recognize more than one mRNA codon. Based on this chapter's discussion of wobble, what is the minimal number of tRNA molecules necessary to recognize the following amino acids?
Leucine

Verified step by step guidance

Understand the concept of wobble: Wobble refers to the flexibility in base pairing at the third position of the codon, allowing a single tRNA to recognize multiple codons. This is due to non-standard base pairing rules at the third position.

Identify the codons for leucine: Leucine is encoded by six codons in the genetic code: UUA, UUG, CUU, CUC, CUA, and CUG.

Group the codons based on wobble compatibility: The codons can be grouped based on their third-base wobble pairing. For example, UUA and UUG can be recognized by one tRNA, while CUU, CUC, CUA, and CUG can be recognized by another tRNA.

Determine the minimal number of tRNAs: Analyze the wobble rules and groupings to determine how many distinct tRNAs are required to recognize all six codons for leucine. Consider the base pairing flexibility at the third position.

Conclude the minimal number of tRNAs: Based on the grouping and wobble rules, calculate the minimal number of tRNAs necessary to recognize all leucine codons without specifying the final number.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Wobble Hypothesis

The wobble hypothesis explains how the third position of a codon can pair with multiple tRNA anticodons, allowing a single tRNA to recognize more than one codon. This flexibility in base pairing is crucial for efficient protein synthesis, as it reduces the number of tRNA molecules needed to translate the genetic code.

Codons and Amino Acids

Codons are sequences of three nucleotides in mRNA that specify particular amino acids during protein synthesis. Each amino acid can be encoded by multiple codons, which is particularly true for leucine, which has six different codons. Understanding the relationship between codons and their corresponding amino acids is essential for determining the number of tRNAs required.

tRNA Molecules

Transfer RNA (tRNA) molecules are responsible for bringing the appropriate amino acids to the ribosome during translation. Each tRNA is specific to one amino acid and can recognize one or more codons due to the wobble effect. The number of distinct tRNA molecules needed depends on the number of unique codons for a given amino acid, factoring in wobble pairing.

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Related Practice

Textbook Question

Predict the amino acid sequence produced during translation by the following short hypothetical mRNA sequences (note that the second sequence was formed from the first by a deletion of only one nucleotide):

Sequence 1: 5'-AUGCCGGAUUAUAGUUGA-3'

Sequence 2: 5'-AUGCCGGAUUAAGUUGA-3'

What type of mutation gave rise to sequence 2?

699

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Textbook Question

Third-base wobble allows some tRNAs to recognize more than one mRNA codon. Based on this chapter's discussion of wobble, what is the minimal number of tRNA molecules necessary to recognize the following amino acids?

Lysine

Isoleucine

Arginine

A short RNA molecule was isolated that demonstrated a hyperchromic shift, indicating secondary structure. Its sequence was determined to be

5'-AGGCGCCGACUCUACU-3'

If the molecule were an internal part of a message, what amino acid sequence would result from it following translation?

440

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Textbook Question

A short RNA molecule was isolated that demonstrated a hyperchromic shift, indicating secondary structure. Its sequence was determined to be

5'-AGGCGCCGACUCUACU-3'

If the molecule were a tRNA fragment containing a CGA anticodon, what would the corresponding codon be?

493

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Textbook Question

The genetic code contains 61 codons to specify the 20 common amino acids. Many organisms carry fewer than 61 different tRNA genes in their genomes. These genomes take advantage of isoaccepting tRNAs and the rules governing third-base wobble to encode fewer than 61 tRNA genes. Use these rules to calculate the minimal number of tRNA genes required to specify all 20 of the common amino acids.

571

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Textbook Question

Shown here is a hypothetical viral mRNA sequence:

5'-AUGCAUACCUAUGAGACCCUUGGA-3'

Assuming that it could arise from overlapping genes, how many different polypeptide sequences can be produced? What are the sequences?

460

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