Why does cytosine make pair with guanine and not with adenine ?

Why does bytosine make pair with guanine and not with adenine ?

Assertion : The two strands in DNA are complementary. Reason : Cytosine always pasirs with guanine and thymine with adenine.

In DNA helix, cytosine is paired with guanine by

Why adenine always pairs with thymine and guanine with cytosine ?

(A) Thymine pairs with adenine whereas cytosine pairs with guanine in DNA molecule. (R) The hydrogen bonding between bases of two strands is highly specific.

Assertion:In a DNA molecules the total quantity of purines equals the total quantity of pyrimidines Reason : Adenine pairs with thymine and cytosine pairs with guanine

Assertion:In a DNA molecules the total quantity of purines equals the total quantity of pyrimidines Reason : Adenine pairs with thymine and cytosine pairs with guanine

Assertion (A): The DNA has two complementary strands. Reason (R): Adenine always pairs with thymine and guanine with cytosine.