A DNA shift, more accurately referred to as a frameshift mutation, is a type of genetic mutation caused by the insertion or deletion of nucleotide bases in a DNA sequence. This insertion or deletion shifts the reading frame of the gene during translation.
Understanding Frameshift Mutations
Here's a breakdown:
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Normal DNA Translation: DNA is read in triplets (codons), each coding for a specific amino acid.
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The Problem: When nucleotides are inserted or deleted (other than in multiples of three), the reading frame is altered.
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The Result: The mRNA sequence downstream of the mutation is read incorrectly. This leads to a completely different amino acid sequence from the original, which can result in a non-functional protein.
Types of Frameshift Mutations
Frameshift mutations occur due to:
- Insertions: Adding one or more nucleotide bases into the DNA sequence.
- Deletions: Removing one or more nucleotide bases from the DNA sequence.
Example of a Frameshift Mutation
Imagine a DNA sequence that reads:
THE BIG CAT ATE
If we delete the "B", the sequence becomes:
THE IGC ATA TE
The meaning is completely changed due to the shift in how the "words" (codons) are read.
Consequences of Frameshift Mutations
- Non-functional protein: The altered amino acid sequence usually renders the protein useless.
- Premature stop codon: The frameshift can lead to a stop codon being encountered prematurely, resulting in a truncated (shortened) protein.
- Disease: Frameshift mutations are associated with various genetic diseases.
Summary Table
| Feature | Description |
|---|---|
| Type of Mutation | Insertion or deletion |
| Effect | Shifts the reading frame of the DNA sequence |
| Result | Altered amino acid sequence, often leading to non-functional or truncated protein |
| Consequences | Can cause genetic diseases |
