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 ?

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

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