Question

Which pair of sequences below might be contained at the ends of an insertion sequence in bacteria?

5′-ATCAGCATC-3′ and 5′-ATCAGCATC-3′

5′-GCGTATAC-3′ and 5′-GTATACGC-3′

5′-GCTTACATG3′ and 5′-GCTTACATG-3′

5'-GGCAGCTCG-3' and 5′-CCGTCGAGC-3′

5′-CCAGCTGAC-3′ and 5′-CAGTCGAGC-3′

Answer 1

In bacterial insertion sequences, the terminal ends are inverted repeats. The correct pair that demonstrates this feature is the sequences 5′-GCGTATAC-3′ and 5′-GTATACGC-3′ because they are reverse complements of each other.

Step-by-step explanation:

The pair of sequences in bacteria that might be contained at the ends of an insertion sequence (IS elements) are usually inverted repeats of one another. This means that they are reverse complements of each other (– they have complementary nucleotides and are oriented in opposite directions). From the options provided, only one pair follows this rule: 5′-GCGTATAC-3′ and 5′-GTATACGC-3′. The ends of the sequences are inverse complements, meaning one strand runs in the 5' to 3' direction and the complementary strand runs in the 3' to 5' direction, but they have the same sequence when read in the 5' to 3' direction. The correct sequences show the typical characteristic of terminal inverted repeats associated with insertion sequences.