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Magazine Chapter 14: Problem 29
Which type of point mutation would have no effect on gene expression? a. frame shift b. missense c. nonsense d. silent
Short Answer
Expert verified
Silent mutation.
Step by step solution
01
Understand Point Mutations
Point mutations are changes in a single nucleotide base in the DNA sequence. There are several types of point mutations: frame shift, missense, nonsense, and silent mutations.
02
Frame Shift Mutation
Frame shift mutations involve the insertion or deletion of a nucleotide, which shifts the reading frame of the genetic code. This typically results in a completely different sequence of amino acids.
03
Missense Mutation
Missense mutations substitute one nucleotide for another, resulting in the change of a single amino acid in the protein sequence. This can affect protein function depending on the amino acid change.
04
Nonsense Mutation
Nonsense mutations change a codon that codes for an amino acid to a stop codon, prematurely terminating protein synthesis. This usually results in a nonfunctional protein.
05
Silent Mutation
Silent mutations are changes in a nucleotide base that do not change the amino acid sequence of the protein. This is because the genetic code is degenerate, meaning some amino acids are encoded by multiple codons.
06
Conclusion
Among the mutation types listed, silent mutations are the ones that typically have no effect on gene expression because they do not alter the amino acid sequence of the protein.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Frame Shift Mutation
A frame shift mutation occurs when there is an insertion or deletion of a nucleotide in the DNA sequence. This alters the reading frame of the genetic code. The reading frame is like a sentence where every three letters form a word. If you add or remove a letter, the whole sentence changes.
For example, the sequence 'THE CAT ATE' could become 'THC ATA TE' if an 'E' is deleted. This causes a completely different set of amino acids to be produced, usually resulting in nonfunctional or harmful proteins. Frame shift mutations can have severe effects on the organism.
For example, the sequence 'THE CAT ATE' could become 'THC ATA TE' if an 'E' is deleted. This causes a completely different set of amino acids to be produced, usually resulting in nonfunctional or harmful proteins. Frame shift mutations can have severe effects on the organism.
Missense Mutation
Missense mutations are when a single nucleotide is changed, causing a different amino acid to be inserted into the protein sequence.
This can have varied effects on the protein's function. Sometimes, the protein might remain functional if the changed amino acid is similar to the original one. But other times, it can significantly alter protein function and lead to diseases or disorders.
For example, sickle cell anemia is caused by a missense mutation where the amino acid glutamic acid is replaced by valine in the hemoglobin protein.
This can have varied effects on the protein's function. Sometimes, the protein might remain functional if the changed amino acid is similar to the original one. But other times, it can significantly alter protein function and lead to diseases or disorders.
For example, sickle cell anemia is caused by a missense mutation where the amino acid glutamic acid is replaced by valine in the hemoglobin protein.
Nonsense Mutation
Nonsense mutations change a normal codon into a stop codon. This causes the translation process to stop prematurely.
The resulting protein is usually shorter and nonfunctional because it lacks essential amino acids that would normally be added to the protein sequence.
For instance, some types of cystic fibrosis are caused by nonsense mutations, leading to nonfunctional proteins that cause disease symptoms.
The resulting protein is usually shorter and nonfunctional because it lacks essential amino acids that would normally be added to the protein sequence.
For instance, some types of cystic fibrosis are caused by nonsense mutations, leading to nonfunctional proteins that cause disease symptoms.
Silent Mutation
Silent mutations are called 'silent' because they do not affect the amino acid sequence of the protein. This is due to the redundancy of the genetic code where multiple codons encode the same amino acid.
For example, if the codon 'GAA' (which codes for glutamic acid) is changed to 'GAG', the amino acid remains glutamic acid. Therefore, the protein remains unchanged, and its function is typically not impaired.
This is why silent mutations often have no effect on gene expression or an organism's phenotype.
For example, if the codon 'GAA' (which codes for glutamic acid) is changed to 'GAG', the amino acid remains glutamic acid. Therefore, the protein remains unchanged, and its function is typically not impaired.
This is why silent mutations often have no effect on gene expression or an organism's phenotype.
Gene Expression
Gene expression refers to the process by which information from a gene is used to synthesize a functional gene product, like a protein. This process includes transcription and translation.
Mutations can affect gene expression in different ways:
Mutations can affect gene expression in different ways:
- Frame shift and nonsense mutations often lead to nonfunctional proteins, severely affecting gene expression.
- Missense mutations can alter the function of the resulting protein, potentially impacting cellular processes.
- Silent mutations typically have no effect on gene expression because they do not change the protein sequence.
