Textbook Question
Explain why it is not feasible to insert the entire human insulin gene into E. coli and anticipate the production of insulin.
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11. Translation
The Genetic Code
2:13 minutesProblem 29e
Textbook Question
Shown here are the amino acid sequences of the wild-type and three mutant forms of a short protein.
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Wild-type: Met-Trp-Tyr-Arg-Gly-Ser-Pro-Thr
Mutant 1: Met-Trp
Mutant 2: Met-Trp-His-Arg-Gly-Ser-Pro-Thr
Mutant 3: Met -Cys-Ile-Val-Val-Val-Gln-His
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Use this information to answer the following questions:
Another mutation (mutant 4) is isolated. Its amino acid sequence is unchanged from the wild type, but the mutant cells produce abnormally low amounts of the wild-type proteins. As specifically as you can, predict where this mutation exists in the gene.
Verified step by step guidance1
Step 1: Begin by analyzing the amino acid sequence of mutant 4. Since the sequence is identical to the wild-type protein, the mutation does not affect the coding region of the gene responsible for the amino acid sequence.
Step 2: Consider the possibility that the mutation affects regulatory regions of the gene. Regulatory regions include the promoter, enhancer, or silencer sequences, which control the transcription of the gene.
Step 3: Evaluate the role of the promoter region. A mutation in the promoter could reduce the binding efficiency of RNA polymerase, leading to lower transcription levels and, consequently, reduced protein production.
Step 4: Investigate post-transcriptional regulation. The mutation could be in regions such as the 5' untranslated region (UTR) or 3' UTR, which influence mRNA stability, translation efficiency, or ribosome binding.
Step 5: Consider epigenetic factors. The mutation might alter chromatin structure or DNA methylation patterns near the gene, reducing accessibility for transcription machinery and leading to lower protein production.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Gene Structure and Function
Genes are segments of DNA that encode proteins, consisting of exons (coding regions) and introns (non-coding regions). The sequence of nucleotides in a gene determines the amino acid sequence of the corresponding protein. Mutations can occur in various parts of the gene, affecting protein production and function. Understanding the structure of genes is crucial for predicting the effects of mutations.
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Types of Mutations
Mutations can be classified into several types, including point mutations, insertions, deletions, and frameshift mutations. A point mutation may change a single nucleotide, potentially altering the amino acid sequence. In this case, the mutation in mutant 4 does not change the amino acid sequence but may affect regulatory elements, leading to decreased protein production. Recognizing these types helps in predicting mutation effects.
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Regulatory Elements
Regulatory elements are sequences in the gene that control the timing and level of gene expression. These include promoters, enhancers, and silencers. A mutation in these regions can lead to changes in how much protein is produced, even if the coding sequence remains unchanged. In the case of mutant 4, the mutation likely resides in a regulatory region, affecting the transcription of the wild-type protein.
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