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What type of mutation occurs when a stop codon replaces an amino acid codon?
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A point mutation that changes a codon specifying an amino acid into a stop codon is called a?
nonsense mutation
Is it possible for mutations to go unnoticed in mRNA?
Yes it is. There are more triplet codons than there are [biologically active] amino acids that need to be represented in the Cell, so that there is some duplication of codon/amino acid 'alignment'. This occurs only in the third base position of the triplet codon - the 'wobble base' position - so if a mutation occurred in the wobble (third) position and the codon was one of the few that was not alone in its amino acid specificity this mutation would go unnoticed.
How is it possible for gene with a mutation in coding region to encode a polypeptide with the same amino acid sequence as the nonmutant gene?
A mutation in the third position of a codon (silent mutation) can result in the same amino acid being encoded due to the redundancy of the genetic code. Since multiple codons can code for the same amino acid, a mutation may not change the amino acid sequence despite occurring in the coding region of the gene.
Why does mrna mutation affect the amino acid sequence?
The codon UGU codes for the amino acid Cysteine. The codon UGG codes for the amino acid Tryptophan. Therefore the mutation will cause the amino acid Cysteine to be replaced with Tryptophan. These amino acids are quite different, and the final shape of the protein could be changed as a result. This could affect the function of the protein.
Why would an insertion or deletion mutation have more effect than a substitution mutation?
Base-pair insertions have a greater effect because they shift the information on the DNA down and change all following information, whereas substitutions may change only one amino acid or have no effect. -The base-pairs code for amino acids in groups of three. If just one base is added in, then this grouping is shifted upstream by one. The incorrect amino acids will be coded for and added to the protein being built. It could possibly stop the protein from being synthesized fully if the change creates a stop codon. This usually hinders the protein from functioning. -Base-pair substitution mutations only affect the codon (set of 3 base pairs) that it actually occurs in. If the mutation is in the first base-pair of the codon then the amino acid will change. If the mutation is in the second or third position of the codon then amino acid may or may not change; this is because amino acids can be coded for by more than one codon, but the first base-pair (and sometimes the second) is usually the same. A substitution can also change a codon to a stop codon. This may keep the amino acid the same, change only one amino acid (which does not always stop the protein from working), or cause the protein to prematurely stop being built.
Which type of mutation occurs when one base replaces another base in a DNA condon?
A point mutation occurs when one base replaces another base in a DNA codon. This type of mutation can result in a different amino acid being incorporated into the protein sequence, which may affect the structure and function of the protein. Examples of point mutations include substitutions, insertions, and deletions of a single base pair.
A point mutation that changes a codon specifying an amino acid into a stop codon is called a?
nonsense mutation
What amino acid is coded for by this sequence before mutation?
The neutral mutation does not change the amino acid coded for by the codon. A good example is the RNA codon that could be the CCA, CCC or the CCG.
When would a mutation in DNA not cause a change in how the gene is expressed or in which proteins are made?
If a point mutation occurs in a location that is not critical to the structure and function of the protein, it will not change the way the gene is expressed. Also, since most amino acids have more than one codon, if the point mutation resulted in a codon for the same amino acid without the mutation, it will not change the way the gene is expressed.
Is it possible for mutations to go unnoticed in mRNA?
Yes it is. There are more triplet codons than there are [biologically active] amino acids that need to be represented in the Cell, so that there is some duplication of codon/amino acid 'alignment'. This occurs only in the third base position of the triplet codon - the 'wobble base' position - so if a mutation occurred in the wobble (third) position and the codon was one of the few that was not alone in its amino acid specificity this mutation would go unnoticed.
How does a nonsense suppressor mutation prevent amber mutants from terminating their polypeptides prematurely?
A nonsense suppressor mutation allows the ribosome to read through a premature stop codon (such as the amber mutation) and continue translating the mRNA. This mutation could change a tRNA's anticodon sequence to recognize the premature stop codon as an amino acid codon, preventing termination and allowing the polypeptide to be elongated instead.
How is it possible for gene with a mutation in coding region to encode a polypeptide with the same amino acid sequence as the nonmutant gene?
A mutation in the third position of a codon (silent mutation) can result in the same amino acid being encoded due to the redundancy of the genetic code. Since multiple codons can code for the same amino acid, a mutation may not change the amino acid sequence despite occurring in the coding region of the gene.
A genetic mutation that causes a codon that should code for a specific amino acid to be changed into a stop codon results in a shortened protein product and is known as?
A premature stop codon mutation, also known as a nonsense mutation. This mutation causes the translation of the protein to be halted prematurely, leading to a truncated and often nonfunctional protein product.
Why does mrna mutation affect the amino acid sequence?
The codon UGU codes for the amino acid Cysteine. The codon UGG codes for the amino acid Tryptophan. Therefore the mutation will cause the amino acid Cysteine to be replaced with Tryptophan. These amino acids are quite different, and the final shape of the protein could be changed as a result. This could affect the function of the protein.
When is a single base substitution mutation least likely to be deleterious?
A single base substitution mutation is least likely to be deleterious when it occurs in a non-coding region of DNA, such as in an intron or in a region with no functional significance. Additionally, if the mutation results in a silent or synonymous change in the amino acid sequence, it may not have a noticeable effect on the protein's function.
Which mutation would not change the remainder of the reading frame of a gene sequence that follows the mutation?
A silent mutation, where a nucleotide substitution results in a codon that codes for the same amino acid, would not change the remainder of the reading frame of a gene sequence. This is because the amino acid sequence produced by the altered codon remains the same.
What amino acid is coded for by this sequence before the mutation?
The amino acid coded for by the original sequence can be determined based on the codon table. The sequence is comprised of sets of three nucleotides that correspond to specific amino acids, so you would need to convert the sequence into codons and then use the table to identify the amino acid coded for by those codons.
