If a phosphate group is also found esterified to the sugar they are called nucleotides.

When heterocyclic rings are attached to a sugar, they are called nucleosides.Living organisms have a number of carbon compounds in which heterocyclic rings can be found.Respiratory System – NCERT General Science.Human Digestive System | Digestive Glands.Animal Tissues – Epithelium, Connective Tissues.Vitamins and Minerals – Deficiency Diseases.Carbohydrates | Monosaccharides | Polysaccharides.Functional segments of dna are called genes. DNA molecules contain the information necessary for constructing and organizing cells.Chromosomes contain information for inheritance of features from parents to next generation in the form of DNA (deoxyribo nucleic acid) molecules. Chromosomes are composed of DNA and Protein.Chromosomes are visible as rod-shaped structures only when the cell is about to divide.Whenever the cell is about to divide, the chromatin material gets organized into chromosomes.Each nucleosome is composed of a little less than two turns of DNA wrapped around a set of eight proteins called histones. The nucleosomeis the fundamental subunit of chromatin.Chromatin material is visible as entangled mass of thread like structures. In a cell which is not dividing, dna is present as part of chromatin material.It controls the transfer of a hereditary characteristic from parents to offspring. Gene is a unit of inheritance in living organisms.The chromosomes can be seen only when the cell divides. These carry genes and help in inheritance or transfer of characters from the parents to the offspring. Nucleus contains thread-like structures called chromosomes.DNA and RNA | Deoxyribonucleic Acid | Ribonucleic Acid – Chromosomes, Nucleotide and Nucleoside, Nucleic acids, DNA and RNA, Recombinant DNA. Source: NCERT Science Textbooks Class 6-12.

Protein backbone versus dna