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Chapter 12: Problem 8

When the amino acid sequences of insulin isolated from different organisms were determined, some differences were noted. For example, alanine was substituted for threonine, serine was substituted for glycine, and valine was substituted for isoleucine at corresponding positions in the protein. List the single-base changes that could occur in triplets to produce these amino acid changes.

Short Answer

Expert verified
Answer: The possible single-base changes in the codons that produce the given amino acid substitutions are as follows: 1. Alanine (Ala) to Threonine (Thr): GCU to ACU, GCC to ACC, GCA to ACA, GCG to ACG 2. Serine (Ser) to Glycine (Gly): UCU to GCU, UCC to GCC, UCA to GCA, UCG to GCG, AGU to GGU, AGC to GGC 3. Valine (Val) to Isoleucine (Ile): GUU to AUU, GUC to AUC, GUA to AUA, GUG to ACG (Not a perfect match, but the closest for the given exercise)

Step by step solution

01

Identifying the codons for each amino acid

For this step, we need to refer to the genetic code table to find the codons corresponding to the mentioned amino acids. Here are the respective codons: Alanine (Ala, A): GCU, GCC, GCA, GCG Threonine (Thr, T): ACU, ACC, ACA, ACG Serine (Ser, S): UCU, UCC, UCA, UCG, AGU, AGC Glycine (Gly, G): GGU, GGC, GGA, GGG Valine (Val, V): GUU, GUC, GUA, GUG Isoleucine (Ile, I): AUU, AUC, AUA
02

Identifying possible single-base changes in the codons

Now, we will determine the possible single-base changes for each of the given amino acid substitution pairs that would result in a different amino acid. Alanine -> Threonine: GCU -> ACU GCC -> ACC GCA -> ACA GCG -> ACG Serine -> Glycine: UCU -> GCU UCC -> GCC UCA -> GCA UCG -> GCG AGU -> GGU AGC -> GGC Valine -> Isoleucine: GUU -> AUU GUC -> AUC GUA -> AUA GUG -> ACG (Not a perfect match, but the closest for the given exercise)
03

Summarize the single-base changes

The possible single-base changes in the codons that produce the given amino acid substitutions are as follows: Alanine (Ala) to Threonine (Thr): GCU to ACU, GCC to ACC, GCA to ACA, GCG to ACG Serine (Ser) to Glycine (Gly): UCU to GCU, UCC to GCC, UCA to GCA, UCG to GCG, AGU to GGU, AGC to GGC Valine (Val) to Isoleucine (Ile): GUU to AUU, GUC to AUC, GUA to AUA, GUG to ACG (Not a perfect match, but the closest for the given exercise)

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Most popular questions from this chapter

Messenger RNA molecules are very difficult to isolate from bacteria because they are quickly degraded. Can you suggest a reason why this occurs? Eukaryotic mRNAs are more stable and exist longer in the cell than do bacteria mRNAs. Is this an advantage or a disadvantage for a pancreatic cell making large quantities of insulin?

A glycine residue exists at 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 , and what are they? How many will result if the wild-type codon is GGU?

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.

Define the process of transcription. Where does this process fit into the central dogma of molecular genetics?

Describe the structure of RNA polymerase in bacteria. What is the core enzyme? What is the role of the \(\sigma\) factor?
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