Question

Which of the following DNA strands can form a DNA duplex by pairing itself at each position?

(a) 5' AAGCCCAA-3'
(b) 5' AAGCCCGTT-3'
(c) 5' AAGCGCAA-3'
(d) 5' AAGCGCTT-3'

Answer 1

The DNA strand that can form a DNA duplex by pairing with itself at each position is option (d) 5' AAGCGCTT-3', as it is the only sequence that follows the base pairing rules and has a palindromic property.

Step-by-step explanation:

To determine which of the following DNA strands can form a DNA duplex by pairing with itself at each position, we must look for a sequence that is palindromic, meaning it reads the same forwards and backwards when aligned with its complementary sequence. DNA strands pair by specific base pairing rules where adenine (A) pairs with thymine (T) and cytosine (C) pairs with guanine (G).

The only sequence in the options that follows this pattern is:

• (d) 5' AAGCGCTT-3'

This strand can fold in the middle to form a duplex, as each base is complementary to the one across from it:

• A (5' end) pairs with T (3' end)
• A pairs with T
• G pairs with C
• C pairs with G
• It reverses from here

None of the other sequences have this exact palindromic property and cannot pair with themselves at each position to form a double strand.