Question

In a DNA molecule, the phosphate group is attached to__________ carbon of the sugar residue of its own nucleotide and ____________ carbon of the sugar residue of the next nucleotide by ______ bonds.
A. 5’, 3’, phosphodiester
B. 5’, 3’, glycosidic
C. 3’, 5’, phosphodiester
D. 3’, 5’, glycosidic

Answer 1

Hint: In living organisms, DNA is an important macromolecule which carries the genetic information and is needed for growth, development and reproduction. In eukaryotic organisms, the DNA is organized into chromosomes which are present inside the nucleus. In bacteria and other prokaryotes, the DNA is present in the cytoplasm.

Complete answer:
DNA is an important nucleic acid and is one of the major molecules that is necessary for all living forms. It is also known as deoxyribonucleic acid. DNA is a large molecule consisting of two polynucleotide chains. The polynucleotide chains are coiled around each other to form a helical structure called the double helix of the DNA.

The strands of DNA are known as the polynucleotide chains. The polynucleotides are made up of much simpler units which are known as the nucleotides. The nucleotide forms the basic structure of the polynucleotides. The nucleotides are made up of bases, a sugar and a phosphate group. The bases are known as the nitrogenous bases as they consist of nitrogen groups in one of their carbon atoms. The DNA molecule consists of four distinct bases which are adenine, guanine, cytosine and thymine.

The nitrogenous bases of the two complementary strands are joined together by specific base pairing and according to it, the adenine always pairs with thymine and cytosine pairs with guanine. The bases form the base pairing by formation of hydrogen bonds.

The nucleotides on the strands are joined together in a chain like structure by formation of covalent bonds which are known as phosphodiester bonds. The phosphodiester bonds join the nucleotides to another between the sugar groups on one nucleotide with the phosphate group of the next nucleotide and so on. This formation by the phosphodiester bond causes the formation of the sugar-phosphate backbone. The sugar group is joined between the third and the fifth carbon atoms of the adjacent sugar rings. The ends are known as the three prime ends and the fife prime ends. The five primer end has a terminal phosphate group and the three primer end has a hydroxyl group. The three prime ends attach with the phosphate group of the next nucleotide.

Hence, The correct answer is option (A).

Note: The DNA is double stranded macromolecule and is found in all living organisms. The long strands of the DNA are coiled around each other to form the double helix structure. The backbone of the DNA molecule is formed by the sugar and the phosphate group. The molecule at its five prime ends contains a terminal phosphate group and the three prime ends join with the adjacent nucleotide through formation of hydrogen bonds.