Chapter 11, Problem 1FTB

DNA consists of subunits called_________. Each subunit consists of three parts:________,________, and_________.

Summary Introduction

To review:

The given blank space in the statement, “deoxyribonucleic acid (DNA) consists of subunits called ______. Each subunit consists of three parts: ____, _____, and _____.

Introduction:

DNA is a molecule which carries of genetic information in all living organisms except few viruses. DNA is a double helix structure formed by base pairs attached to a sugar-phosphate backbone. DNA is wrapped around a protein complex known as histones which further forms chromatin. This complex and organized structure is as a nucleosome in a eukaryotic cell.

Explanation of Solution

Nucleotide: Nucleotides are those organic biomolecules which act as a monomer for building up a long chain of DNA. It is a building block of nucleic acids. Nucleotide is composed of three subunits, namely, a sugar (pentose sugar), nitrogenous bases, and a phosphate group. When a nucleoside attaches with a phosphate group it then forms a nucleotide.

In case of ribonucleic acid (RNA), the pentose sugar is a ribose sugar while in case of DNA sugar is deoxyribose. The pentose sugar structurally lacks an oxygen atom from its two carbon position, thus named as deoxyribose.

Phosphate group: This group is chemically derived from phosphoric acid. When attached to the pentose sugar form a nucleotide. The linkage between the two nucleotides is helped by the phosphate group via a phosphodiester linkage.

Bases: Nitrogenous bases consist of nitrogen, carbon, and hydrogen in their homocyclic and heterocyclic rings. There exist five types of bases: adenine, thymine, guanine, cytosine, and uracil (in case of RNA). They form a strand in a double-helical structure of DNA. Their stability is directed by hydrogen bondings.

Conclusion

DNA consists of subunits called nucleotide. Each subunit consists of three parts: pentose sugar, a phosphate group, and nitrogenous bases.