Introduction
Nucleic acids are polymers of ribonucleotides or
deoxyribonucleotides and are associated with the nucleus
of a cell. DNA and RNA are the important nucleic acids
found in the cells.
Structure
A nucleotide contains a nitrogenous base, phosphate group and sugar.
An organic molecule containing a nitrogenous base called purine or
pyrimidine is present in nucleotide. Purines are adenine or guanine
and pyrimidines are cytosine, thymine or Uracil. Depending on the
number of phosphate groups present in nucleotides, they are known as
nucleotide monophosphates, diphosphates or triphosphates.
Types of nucleic acids
There are two types of nucleic acids, deoxyribonucleic acid and
ribonucleic acid.
DNA
DNA is a very long thread like molecule made up of a very large
number of deoxyribonucleotides joined together. DNA is a linear
double stranded polymer made up of deoxyribonucleotides.
Deoxyribonucleotide is made up of a sugar called deoxyribose, a
nitrogenous base and a phosphate group. DNA is located in the
nucleus. Nucleotides are joined together by a phosphodiester bond in
a condensation reaction. Double helix is formed when two strands are
joined together by hydrogen bonds. Double helix is anti parallel.
Both the stands run in opposite direction and are parallel to each
other.
RNA
RNA is a linear polymer in which nucleotides are linked together by
means of phosphodiester bridges. It does not form a double helix
like DNA. There are three different types of RNA: mRNA, tRNA and
rRNA. Most RNA molecules usually have secondary structure,
consisting of stem and loop domains. mRNA is linear in structure,
variable in size, has a poly A tail and acts as a template for
protein synthesis. tRNA has a clover leaf structure. rRNA is large
in size and is associated with protein. All the three types of RNA
are associated in the production of a protein.
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