Nucleic Acids - DNA and RNA - Practice Questions & MCQ

Nucleic Acids - DNA and RNA

DNA:

• The deoxyribonucleic acid (DNA) is a polymer of deoxynucleotides. 
• The pentose sugar in deoxynucleotides lack the -O at C-2. This is the reason it is called the deoxyribose sugar.

• DNA is a polymer of nucleotides. It means many nucleotides are linked with each other via a covalent bond to form a polymer.
• The covalent bond that links the two nucleotides is called phosphodiester bond. 

• Hence, a polynucleotide chain is formed when many nucleotides are united via the phosphodiester bond.
• A DNA is made up of two polynucleotide chains that are connected with each other via hydrogen bonds.
• The two polynucleotide chains are helically arranged around each other.
• In a polynucleotide chain, the backbone is formed of sugar and phosphate while the nitrogenous bases form hydrogen bonds.
• Adenine forms two hydrogen bonds with thymine.
• Cytosine forms three hydrogen bonds with guanine.

DNA is the genetic material of the living organisms, except for some viruses. It stores hereditary information.

RNA:

• The ribonucleic acid (RNA) is also a polymer of nucleotides.
• The pentose sugar of RNA has -OH group at C-2.
• It is also a polynucleotide chain wherein the nucleotides are linked with each other via the phosphodiester bond.
• Unlike DNA, it is single stranded and more reactive.
• RNA contains uracil as one of the pyrimidines rather than the thymine. 
• RNA acts as genetic material in some viruses.
• In majority of the living organisms, following types of RNA molecules are present:
• mRNA or messenger RNA, carries the message from DNA and forms the polypeptide chain along with the ribosomes.
• Ribosomal RNA (rRNA) is a major constituent of ribosomes on which the mRNA binds.
• Transfer RNA (tRNA) is one of the smallest of the three types of RNA, usually 70–90 nucleotides long. It carries the correct amino acid to the site of protein synthesis.