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Ch. 9 - The Molecular Biology of Translation
Sanders - Genetic Analysis: An Integrated Approach 3rd Edition
Sanders3rd EditionGenetic Analysis: An Integrated ApproachISBN: 9780135564172Not the one you use?Change textbook
Chapter 9, Problem 24b

Har Gobind Khorana and his colleagues performed numerous experiments translating synthetic mRNAs. In one experiment, an mRNA molecule with a repeating UG dinucleotide sequence was assembled and translated.
What is the sequence of the resulting polypeptide?

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1
Understand the problem: The mRNA sequence consists of repeating UG dinucleotides. Translation involves reading the mRNA sequence in codons (groups of three nucleotides) to determine the corresponding amino acids in the polypeptide chain.
Break the repeating UG sequence into codons: Since the sequence is repeating UG (UGUGUG...), the codons formed will alternate between UGU and GUG. This is because translation reads the mRNA in groups of three nucleotides.
Determine the amino acids corresponding to each codon: Use the genetic code table to find the amino acids. For example, UGU codes for cysteine (Cys), and GUG codes for valine (Val).
Analyze the pattern of the polypeptide sequence: Since the mRNA sequence alternates between UGU and GUG, the resulting polypeptide will alternate between cysteine (Cys) and valine (Val).
Conclude the sequence of the polypeptide: The polypeptide will consist of a repeating pattern of cysteine (Cys) and valine (Val), corresponding to the alternating codons in the mRNA sequence.

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Key Concepts

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

mRNA and Codons

Messenger RNA (mRNA) is a type of RNA that carries genetic information from DNA to the ribosome, where proteins are synthesized. The mRNA sequence is read in sets of three nucleotides called codons, each of which corresponds to a specific amino acid. Understanding how codons are formed from nucleotide sequences is essential for predicting the resulting polypeptide.
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mRNA Processing

Translation Process

Translation is the process by which ribosomes synthesize proteins using the information encoded in mRNA. During translation, the ribosome reads the mRNA codons and matches them with the appropriate transfer RNA (tRNA) molecules that carry specific amino acids. This process results in the formation of a polypeptide chain, which eventually folds into a functional protein.
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mRNA Processing

Genetic Code

The genetic code is a set of rules that defines how sequences of nucleotides in mRNA are translated into amino acids. It consists of 64 codons that specify 20 different amino acids, with some amino acids being encoded by multiple codons. Understanding the genetic code is crucial for determining the sequence of the resulting polypeptide from a given mRNA sequence.
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Related Practice
Textbook Question

The amino acid sequence of a portion of a polypeptide is

N...Cys-Pro-Ala-Met-Gly-His-Lys...C

What is the mRNA sequence encoding this polypeptide fragment? Use N to represent any nucleotide, Pu to represent a purine, and Py to represent a pyrimidine. Label the 5′ and 3′ ends of the mRNA.

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Textbook Question

The amino acid sequence of a portion of a polypeptide is

N...Cys-Pro-Ala-Met-Gly-His-Lys...C

Give the DNA template and coding strand sequences corresponding to the mRNA. Use the N, Pu, and Py symbols as placeholders.

712
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Textbook Question

Har Gobind Khorana and his colleagues performed numerous experiments translating synthetic mRNAs. In one experiment, an mRNA molecule with a repeating UG dinucleotide sequence was assembled and translated.

Write the sequence of this mRNA and give its polarity.

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Textbook Question

Har Gobind Khorana and his colleagues performed numerous experiments translating synthetic mRNAs. In one experiment, an mRNA molecule with a repeating UG dinucleotide sequence was assembled and translated.

How did the polypeptide composition help confirm the triplet nature of the genetic code?

873
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Textbook Question

Har Gobind Khorana and his colleagues performed numerous experiments translating synthetic mRNAs. In one experiment, an mRNA molecule with a repeating UG dinucleotide sequence was assembled and translated.

If the genetic code were a doublet code instead of a triplet code, how would the result of this experiment be different?

627
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Textbook Question

Har Gobind Khorana and his colleagues performed numerous experiments translating synthetic mRNAs. In one experiment, an mRNA molecule with a repeating UG dinucleotide sequence was assembled and translated.

If the genetic code were overlapping rather than nonoverlapping, how would the result of this experiment be different?

757
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