The backbone of DNA molecule is made of a. nucleotides  b. alternating phosphates and bases  c. alternating bases and sugars  d. alternating sugar and phosphate molecules
The backbone of DNA molecule is made of?
 a.
nucleotides
 b.
alternating phosphates and bases
 c.
alternating bases and sugars
 d.
alternating sugar and phosphate molecules
The Correct Answer and Explanation is :
The correct answer is d. alternating sugar and phosphate molecules.
Explanation:
The backbone of the DNA molecule is composed of a repeating structure of sugar and phosphate groups. DNA, or deoxyribonucleic acid, consists of two strands that twist together to form a double helix. These strands are made up of smaller subunits called nucleotides, each containing a sugar molecule, a phosphate group, and a nitrogenous base. However, when we refer to the “backbone” of the DNA molecule, we are specifically talking about the structural framework that supports and holds the genetic information in place.
Each nucleotide has a sugar molecule, specifically deoxyribose in the case of DNA, attached to a phosphate group. The sugar and phosphate groups alternate in a regular repeating pattern along the length of each DNA strand. The bond between the phosphate group of one nucleotide and the sugar molecule of the next is called a phosphodiester bond. This alternating sequence of sugars and phosphates forms the structural backbone of the DNA double helix, providing stability and allowing the molecule to maintain its shape.
The nitrogenous bases, which are adenine (A), thymine (T), cytosine (C), and guanine (G), do not form part of the backbone. Instead, these bases extend inward from the sugar-phosphate backbone and form hydrogen bonds with complementary bases on the opposite strand. These base pairs (A-T and C-G) are responsible for encoding genetic information.
Thus, the correct description of the DNA backbone is that it is composed of alternating sugar and phosphate molecules. This structure allows DNA to be both stable and flexible, making it capable of storing and transmitting genetic information across generations.