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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 1a

Some proteins are composed of two or more polypeptides. Suppose the DNA template strand sequence 3′-TACGTAGGCTAACGGAGTAAGCTAACT-5′ produces a polypeptide that joins in pairs to form a functional protein. What is the amino acid sequence of the polypeptide produced from this sequence?

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1
Identify the DNA template strand sequence provided: 3′-TACGTAGGCTAACGGAGTAAGCTAACT-5′.
Determine the complementary mRNA sequence by transcribing the DNA template strand. Remember that RNA uses uracil (U) instead of thymine (T). The complementary mRNA sequence will be 5′-AUGCAUCCGAUUGCCUCAUUCGAUUGA-3′.
Divide the mRNA sequence into codons (groups of three nucleotides), starting from the 5′ end. For example: AUG, CAU, CCG, etc.
Use the genetic code to translate each codon into its corresponding amino acid. For instance, AUG codes for methionine (start codon), and so on. Continue translating until you encounter a stop codon (e.g., UGA).
Write down the amino acid sequence produced from the translation process. This sequence represents the polypeptide that will pair with another identical polypeptide to form the functional protein.

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Key Concepts

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

DNA Transcription

DNA transcription is the process by which a segment of DNA is copied into RNA by the enzyme RNA polymerase. The DNA template strand is read in the 3' to 5' direction, and the resulting RNA strand is synthesized in the 5' to 3' direction. This process is crucial for producing messenger RNA (mRNA), which carries the genetic information from DNA to the ribosome for protein synthesis.
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Prokaryotic Transcription

Translation and Codons

Translation is the process by which the mRNA sequence is decoded to synthesize a polypeptide chain. The mRNA is read in sets of three nucleotides called codons, each of which corresponds to a specific amino acid. Understanding the genetic code, which maps codons to amino acids, is essential for determining the amino acid sequence of the resulting polypeptide.
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Translation initiation

Polypeptide Structure

Polypeptides are chains of amino acids linked by peptide bonds, and they can fold into specific three-dimensional structures to form functional proteins. The sequence of amino acids, determined by the mRNA, dictates how the polypeptide will fold and function. In the context of the question, knowing how polypeptides can join in pairs to form functional proteins is important for understanding protein structure and function.
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Related Practice
Textbook Question

Answer the following questions for autosomal conditions such as PKU.

Parents who are each heterozygous carriers for a recessive mutant allele have a child who does not have the condition. What is the chance this child is a heterozygous carrier of the condition?

Textbook Question

Answer the following questions for autosomal conditions such as PKU.

If the first child of parents who are both heterozygous carriers of a recessive mutant allele is homozygous recessive, what is the chance the second child of the couple will be homozygous recessive? What is the chance the second child will be a heterozygous carrier of the recessive mutation?

1
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Textbook Question

Answer the following questions for autosomal conditions such as PKU.

If both parents are heterozygous carriers of a mutant allele, what is the chance that their first child will be homozygous recessive for the mutation?

3
views
Textbook Question

Some proteins are composed of two or more polypeptides. Suppose the DNA template strand sequence 3′-TACGTAGGCTAACGGAGTAAGCTAACT-5′ produces a polypeptide that joins in pairs to form a functional protein.

What term is used to identify a functional protein like this one formed when two identical polypeptides join together?

Textbook Question

Homocystinuria is a rare autosomal recessive condition on the RUSP list of conditions screened by newborn genetic testing. The condition results from a mutation that blocks the degradation of the amino acid methionine. The absence of a critical enzyme causes the buildup of the compound homocysteine, which is one of the intermediate compounds in the methionine breakdown pathway. Homocystinuria causes mental impairment, heart problems, seizures, eye abnormalities, and a number of other symptoms that shorten life if not treated. The condition is treated by a specialized diet that is low in methionine and by the ingestion of several supplements.

The low-methionine diet must be maintained throughout life to manage homocystinuria. Why do you think this is the case?

Textbook Question

Homocystinuria is a rare autosomal recessive condition on the RUSP list of conditions screened by newborn genetic testing. The condition results from a mutation that blocks the degradation of the amino acid methionine. The absence of a critical enzyme causes the buildup of the compound homocysteine, which is one of the intermediate compounds in the methionine breakdown pathway. Homocystinuria causes mental impairment, heart problems, seizures, eye abnormalities, and a number of other symptoms that shorten life if not treated. The condition is treated by a specialized diet that is low in methionine and by the ingestion of several supplements.

Why do you think eating a low-methionine diet is critical to controlling homocystinuria?