Question

select the correct answer.

which type of mutation does the change in this nucleotide sequence represent?

gcttagcgc \\(\
ightarrow\\) gcttatagcgc

• duplication
• inversion
• substitution
• translocation

Explanation:

Compare the original and mutated sequences

We align the original sequence with the mutated sequence to identify the exact change:

• Original: G C T T A G C G C (9 nucleotides)
• Mutated: G C T T A T A G C G C (11 nucleotides)

Identify the inserted segment

By aligning the sequences, we see:

• Original: G C T T A _ _ G C G C
• Mutated: G C T T A T A G C G C

The nucleotides T A have been inserted after the fifth nucleotide A.

Analyze the origin of the insertion

Looking closely at the original sequence:

• The nucleotides at positions 3 and 4 are T T.
• The nucleotides at positions 4 and 5 are T A.
• The inserted sequence is T A, which is an exact copy of the adjacent preceding sequence T A (positions 4 and 5).
• When a sequence of nucleotides is repeated or copied adjacent to the original, it is classified as a duplication.

Evaluate the given options

• duplication: Correct, as the segment TA is duplicated.
• inversion: Incorrect, as no segment is reversed in orientation.
• substitution: Incorrect, as the sequence length increased and no bases were replaced.
• translocation: Incorrect, as this does not involve a segment moving to a non-homologous chromosome.

Answer:

• duplication (Correct answer)
• inversion
• substitution
• translocation