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A DNA segment has base order CCC ATA GCT. Which copy exhibits a deletion in the first codon triplet and then a substitution mutation?(1 point)

Responses

CCA ATA GCT
CCA ATA GCT

CCA TAG CT
CCA TAG CT

CCC TAG CT
CCC TAG CT

CCA TAA CT

1 answer

To analyze the provided mutations in response to the original DNA segment "CCC ATA GCT," let's break it down.

  1. The original DNA segment consists of the following codons:

    • CCC
    • ATA
    • GCT

  2. A deletion in the first codon triplet means that one of the bases in "CCC" must be removed.

  3. A substitution mutation in the context of this question can be either a change in one of the bases in the remaining sequence after the deletion or in the first codon triplet after the deletion.

Evaluating the responses:

  1. Response 1: CCA ATA GCT

    • The first codon "CCC" has undergone a deletion (the first C has been removed), which becomes "CA" and is not a triplet anymore, but there is no substitution.

  2. Response 2: CCA TAG CT

    • Again, "CCC" has become "CA" and one base has been deleted, followed by "TAG" which is a substitution in place of "ATA." This satisfies the criteria of a deletion in the first codon and a substitution in the second codon.

  3. Response 3: CCC TAG CT

    • "CCC" remains unchanged (no deletion occurred), and "ATA" has been substituted with "TAG," which does not fit the criteria for deletion.

  4. Response 4: CCA TAA CT

    • "CCC" becomes "CA," which is a deletion; however, "ATA" has been substituted with "TAA." This also meets one deletion and a substitution.

Since we need only one option that fulfills the criteria of having a deletion in the first codon triplet and a substitution mutation, Response 2: CCA TAG CT is the best fit as it includes both the deletion and the substitution distinctly.

Thus, the correct answer is:

CCA TAG CT