Question

Choose the correct answers from the alternatives given :
Which of the following regarding DNA is not true?

• A. Complementary base pairs consist of one purine and one pyrimidine
• B. Side rails of the DNA double helix are made of alternating molecules of phosphate and ribose
• C. Complementary base pairs are joined by hydrogen bonds
• D. Amount of thymine equals the amount of adenine

Answer 1

The correct option is B Side rails of the DNA double helix are made of alternating molecules of phosphate and ribose

According to the chargaff's rule the amount of purine is equal to the amount of pyrimidine in a DNA. The base pairing that occurs in DNA is complementary such that A bonds with T and G bonds with C, vice verse is also true. The complementary base pairs like A and T are joined with each other by double hydrogen bonds while G and C are bonded to each other with triple hydrogen bonds. The DNA double helix side rails are made of alternating phosphate and deoxyribose sugar molecules

So, the correct option is 'Side rails of the DNA double helix are made of alternating molecules of phosphate and ribose'.