Refer to Table 8.2. If a frameshift mutation occurred in the sequence of bases shown below, what would be the sequence of amino acids coded?
```
3'ATTACGCTITGC
```
Codon on mRNA and corresponding amino acid
| UUA | leucine | UAA | nonsense |
| :------- | :------- | :-- | :------- |
| GCA | alanine | AAU | sparagine|
| AAG | lysine | UGC | cysteine |
| GUU | valine | UCG, UCU | serine |
A. asparagine-arginine-lysine-alanine
B. asparagine-cysteine-valine-serine
C. leucine-arginine-lysine-alanine
D. Translation would stop at the first codon.
E. The answer cannot be determined based on the information provided.
Answer (1)
Transcribe the DNA sequence to mRNA: 5'CGCAAUCGAAAU.
Assume an insertion frameshift mutation: 5'XCGCAAUCGAAAU.
Divide the sequence into codons: CGA, AUC, GAA, AU.
Since none of these codons are in the table, the answer cannot be determined. The answer cannot be determined based on the information provided.
Explanation
Analyze the problem Let's analyze the problem. We are given a DNA sequence 3'ATTACGCTITGC and a table of mRNA codons with corresponding amino acids. A frameshift mutation occurs, and we need to determine the resulting amino acid sequence.
Transcribe DNA to mRNA First, we need to transcribe the DNA sequence into mRNA. Remember that during transcription, adenine (A) pairs with uracil (U), thymine (T) pairs with adenine (A), guanine (G) pairs with cytosine (C), and cytosine (C) pairs with guanine (G). Also, the mRNA sequence is read from 5' to 3', which is the reverse of the given DNA sequence. Thus, the mRNA sequence corresponding to 3'ATTACGCTITGC is 5'CGCAAUCGAAAU.
Consider frameshift mutation Now, let's consider a frameshift mutation. Since the type of frameshift mutation is not specified (insertion or deletion), let's assume an insertion of one base (X) at the beginning of the sequence. The new mRNA sequence becomes 5'XCGCAAUCGAAAU.
Divide mRNA into codons Next, we divide the new mRNA sequence into codons (groups of three bases), starting from the 5' end. Since we don't know what X is, we'll consider two cases:
Case 1: Ignore the unknown base X. The codons are: CGA, AUC, GAA, AU(end). Case 2: Assume the frameshift is a deletion of the first base. The codons are: GCA, AUC, GAA, U(end).
However, since the type of frameshift mutation is not specified, we will proceed by assuming the insertion of one base at the beginning of the sequence. This gives us 5'XCGCAAUCGAAAU, where X is an arbitrary base. We will ignore the first codon and start from the second codon. So, we have codons: CGA, AUC, GAA, AU.
Determine amino acid sequence Now, we need to use the given codon table to determine the amino acid sequence corresponding to these codons. The table provides the following codon-amino acid correspondences:
UUA - leucine GCA - alanine AAG - lysine GUU - valine UAA - nonsense AAU - asparagine UGC - cysteine UCG/UCU - serine
None of the codons (CGA, AUC, GAA, AU) are in the table. Therefore, we cannot determine the amino acid sequence based on the information provided.
Conclusion Since none of the codons produced after the frameshift mutation are present in the given table, we cannot determine the resulting amino acid sequence.
Examples
Frameshift mutations can drastically alter the protein produced from a gene. Understanding how these mutations affect the codon sequence is crucial in genetic research and medicine. For example, if a gene responsible for producing a vital enzyme undergoes a frameshift mutation, the resulting non-functional enzyme can lead to a disease. By studying the altered codon sequences, scientists can develop targeted therapies to correct or compensate for the mutation's effects.
