Question

a strand of dna contains the bases adenine, cytosine, cytosine, and guanine, in that order. which would be the order of the bases on the opposite strand of dna?
○ cytosine, adenine, adenine, and thymine
○ cytosine, thymine, thymine, and adenine
○ thymine, guanine, guanine, and cytosine
○ thymine, adenine, adenine, and cytosine

Explanation:

In DNA base pairing, adenine (A) pairs with thymine (T), and cytosine (C) pairs with guanine (G). The given strand is adenine, cytosine, cytosine, guanine. So the opposite strand should have thymine (for adenine), guanine (for cytosine), guanine (for cytosine), and cytosine (for guanine)? Wait, no, wait: Wait, original strand: A, C, C, G. So A pairs with T, C pairs with G, C pairs with G, G pairs with C? Wait no, wait the base pairing is A-T and C-G. So first base: A (adenine) pairs with T (thymine). Second base: C (cytosine) pairs with G (guanine). Third base: C (cytosine) pairs with G (guanine). Fourth base: G (guanine) pairs with C (cytosine)? Wait no, wait the options: Let's check the options. Wait the options are:

1. cytosine, adenine, adenine, and thymine – no, A pairs with T, not C.

1. cytosine, thymine, thymine, and adenine – no, C pairs with G, not T.

1. thymine, guanine, guanine, and cytosine – Let's see: A (first base) pairs with T (thymine) – correct. C (second) pairs with G (guanine) – correct. C (third) pairs with G (guanine) – correct. G (fourth) pairs with C (cytosine) – correct. Wait, but wait, the original strand is A, C, C, G. So opposite strand: T (for A), G (for C), G (for C), C (for G). So that's thymine, guanine, guanine, cytosine – which is option 3. Wait but let me check again. Wait the fourth base: G (guanine) pairs with C (cytosine), yes. So option 3 is thymine, guanine, guanine, and cytosine. Let's check the other options. Option 4: thymine, adenine, adenine, and cytosine – C pairs with G, not A. So option 3 is correct.

Answer:

C. thymine, guanine, guanine, and cytosine (Wait, the options are not labeled with letters, but the third option in the list is "thymine, guanine, guanine, and cytosine". So the correct option is the third one, which is "thymine, guanine, guanine, and cytosine".)