Skip to main content
Pearson+ LogoPearson+ Logo
Ch. 13 - The Genetic Code and Transcription
Klug - Concepts of Genetics 12th Edition
Klug12th EditionConcepts of Genetics ISBN: 9780135564776Not the one you use?Change textbook
All textbooksKlug 12th EditionCh. 13 - The Genetic Code and TranscriptionProblem 15a
Chapter 13, Problem 15a

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?
Codon table showing amino acids for each codon, highlighting start codon AUG and stop codons UAA, UAG, UGA.

Verified step by step guidance
1
Step 1: Identify the three possible reading frames for the given mRNA sequence 5'-AUGCAUACCUAUGAGACCCUUGGA-3'. The reading frames start at nucleotide positions 1, 2, and 3 respectively.
Step 2: For each reading frame, divide the sequence into codons (groups of three nucleotides) starting from the respective position. For example, in frame 1, codons are nucleotides 1-3, 4-6, 7-9, etc.; in frame 2, codons are 2-4, 5-7, 8-10, etc.; and in frame 3, codons are 3-5, 6-8, 9-11, etc.
Step 3: Translate each codon into its corresponding amino acid using the codon table provided. Pay special attention to the start codon AUG (Methionine) which signals the beginning of translation, and the stop codons UAA, UAG, and UGA which signal termination.
Step 4: For each reading frame, identify the polypeptide sequence starting from the first AUG codon encountered and continuing until a stop codon is reached or the sequence ends. If no start codon is found in a frame, no polypeptide is produced from that frame.
Step 5: Compile the polypeptide sequences from all three reading frames to determine how many different polypeptides can be produced and what their amino acid sequences are.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above.
Video duration:
2m
Was this helpful?

Key Concepts

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

Reading Frames and Overlapping Genes

A single mRNA sequence can be read in three different reading frames, depending on the starting nucleotide. Overlapping genes occur when different proteins are encoded by the same nucleotide sequence but in different frames. Understanding reading frames is essential to determine how many distinct polypeptides can be produced from one mRNA.
Recommended video:
Guided course
11:19
Segmentation Genes

Codon Table and Translation

The codon table maps each three-nucleotide codon to a specific amino acid or a stop signal. Translation begins at a start codon (AUG) and ends at a stop codon (UAA, UAG, UGA). Using the codon table, one can translate nucleotide sequences into amino acid sequences to identify possible polypeptides.
Recommended video:
Guided course
07:58
Translation initiation

Start and Stop Codons in Protein Synthesis

Start codons (AUG) signal the beginning of translation, while stop codons (UAA, UAG, UGA) signal its termination. Identifying these codons in each reading frame helps determine the length and sequence of the resulting polypeptides. This is crucial for predicting all possible proteins from overlapping genes.
Recommended video:
Guided course
05:05
Proteins
Related Practice
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?

558
views
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 an internal part of a message, what amino acid sequence would result from it following translation?

520
views
Textbook Question

A glycine residue is in position 210 of the tryptophan synthetase enzyme of wild-type E. coli. If the codon specifying glycine is GGA, how many single-base substitutions will result in an amino acid substitution at position 210? What are they? How many will result if the wild-type codon is GGU?

555
views
Textbook Question

Refer to the genetic coding dictionary to respond to the following:

A base-substitution mutation that altered the sequence shown in part (a) eliminated the synthesis of all but one polypeptide. The altered sequence is shown here:

5'-AUGCAUACCUAUGUGACCCUUGGA-3'

Determine why.

633
views
Textbook Question

Most proteins have more leucine than histidine residues, but more histidine than tryptophan residues. Correlate the number of codons for these three amino acids with this information.

604
views
Textbook Question

Define the process of transcription. Where does this process fit into the central dogma of molecular biology (DNA makes RNA makes protein)?

791
views