Consider the following statements and choose the correct answer:
1. Adenine pairs with thymine (A : T) and guanine with cytosine $$\left( {G \vdots C} \right)$$
2. Adenine and thymine are joined by three hydrogen bonds through atoms
3. Guanine and cytosine are joined by two hydrogen bonds through atoms
4. The weak hydrogen bonding enables the two strands of the DNA to separate during replication

Solution (By Examveda Team)

Let's break down this DNA pairing question!

Statement 1: Adenine pairs with thymine (A : T) and guanine with cytosine (G : C).
This is a fundamental rule of DNA base pairing, so it's TRUE.

Statement 2: Adenine and thymine are joined by three hydrogen bonds.
This is incorrect. Adenine and thymine are joined by TWO hydrogen bonds. So, it's FALSE.

Statement 3: Guanine and cytosine are joined by two hydrogen bonds.
This is also incorrect. Guanine and cytosine are joined by THREE hydrogen bonds. So, it's FALSE.

Statement 4: The weak hydrogen bonding enables the two strands of the DNA to separate during replication.
This is TRUE. The relatively weak hydrogen bonds are essential for DNA replication because they allow the DNA strands to be easily separated so they can be copied.

Therefore, only statements 1 and 4 are true.

The correct answer is Option D: Only 1 and 4 are true.