What is the definition of :
a. Nucleosome
b. Nucleic acid
c. Nucleotide
d. Polynucleotide

Dear Student,

1) When we analyze the structure of eukaryotic chromosome we find that it is composed of DNA and proteins. DNA is negatively charged and to stabilize the system some positively charged (basic) protein molecules called histones are bound to it.There is large amount of DNA in our cells which creates a packaging problem. So, in order to maintain a high degree of organisation, DNA is folded. DNA helix combines with a group of eight histone molecules to form a structure called nucleosome.

2)  Nucleic acids are biological molecules essential for known forms of life on this planet; they include DNA (deoxyribonucleic acid) and RNA (ribonucleic acid). Together with proteins, nucleic acids are the most important biological macromolecules; each is found in abundance in all living things, where they function in encoding, transmitting and expressing genetic information. Nucleic acid is the polymer containing long chains of nucleotides. A nucleotide contains a sugar-phosphate group and nitrogenous bases.

3) Nucleotides are molecules when joined together make up the structural unit of DNA or RNA.

A Nucleotide consist of three parts :

• Sugar: The sugar has 5 carbon atoms, therefore it is called a pentose. It can be ribose or 2'-deoxyribose sugar.
• Nucleobase or nitrogenous base (Purines and pyrimidines)
• One Phosphate group

4) Polynucleotide - Chain formed by joining of many nucleotides is referred to as polynucleotide. Example DNA and RNA. A polynucleotide chain is made up of several nucleotides. Each nucleotide contains a five carbon (pentose) sugar, to which a phosphate group and a nitrogenous base remain attached. There are five common types of nitrogenous bases – adenine, guanine, cytosine, thymine and uracil. Nucleotides are joined by covalent bond between two phosphate groups of two different nucleotides.

 

Hope this information will clear your doubts about the topic. 


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