To identify a frameshift mutation caused by a deletion during replication, we need to look for an option where one or more nucleotides have been removed from the original DNA sequence, leading to a shift in the reading frame for downstream codons.
The original strand of DNA is:
ATG AAG TTT GGC TAA
Now, let's evaluate the options:
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ATG AAG TTG GCT AA
- The "TTT" codon has been changed to "TTG". This is not a deletion; it’s simply a change in one nucleotide and does not constitute a frameshift.
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A T G A A G T T G G C T A A
- This option just breaks down the original sequence into individual nucleotides but doesn't represent a mutation.
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ATG AAG AAG TTT GGC TAA
- Here, an "AAG" was added without any deletion, which does not represent a frameshift mutation.
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ATG AAG TTT GGC CGC ATA A
- In this option, additional nucleotides "CGC ATA" have been added. This does not represent a deletion, hence it’s not a frameshift.
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ATG AAG TTT GGC
- In this option, “TAA” has been removed. This results in a deletion of the codon, which would cause a frameshift in the subsequent reading frame as there’s an alteration in the number of codons.
Based on the above evaluations, the option that represents a frameshift mutation caused by a deletion is:
ATG AAG TTT GGC (last option).
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