DNA constitute an integral component of genes**, whereas, nucleotides designate a macro-molecule made up of repeatable units present in DNA.
Structure
and Function of Genetic Material
DNA constitute an integral component of genes**,
whereas, nucleotides designate a
macro-molecule made up of repeatable units present in DNA. In fact, each nucleotide
essentially comprises of a ‘nitrogenous
base’ viz., adenine (A), thymine (T), cytosine (C), and guanine(G) — besides, a pentose
sugar deoxyribose, together with a ‘phosphate’ moiety. It has been duly
established that within a cell the DNA is invariably present as ‘long strands of nucleotides that are duly
twisted together in pairs to form a
double-helix’.***
Each
strand of DNA prominently bears two
structural features, namely :
(a) a
string of alternating sugar and phosphate moieties, and
(b) a
nitrogenous base attached duly to each sugar moiety in its backbone.
Thus, the
‘pair of strands’ are intimately
held together strategically by means of H-bonds be-tween their respective
nitrogenous bases. However, the ‘pairing
of nitrogenous bases’ are found to be in a specific manner i.e., adenine pairs with thymine
; and cytosine pairs with guanine [either AT or CG pairs]. Due to
this specific base pairing mode, the base sequence of one DNA strand
categorically determines the base
sequence of the other strand. Therefore, one may observe that the strands of
DNA are actually complementary.****
It has already been proved and established that the aforesaid ‘com-plementary structure of DNA’ goes
a long way to expatiate as well as explain the manner by which the DNA actually stores and critically
transmits the so called ‘genetic
information’.
The
functional product is invariably a
messenger RNA (designated as mRNA)
molecule, that eventually results in the formation of a protein. Interestingly, it may also be a ribosomal RNA (i.e., rRNA). It is, however, pertinent to
state here that both these types of RNA (viz., mRNA and rRNA) are prominently involved in the process of protein synthesis.
Genetic Code : It has been duly ascertained that
relevant ‘genetic information’ is
meticulously encoded by the sequence
of bases along a specific strand of DNA, which is almost similar to the usage
of ‘linear sequence of alphabets’ to
first construct ‘words’, and
secondly, the ‘sentences’.
Impor-tantly, the so called ‘genetic
language’ largely makes use of only four
letters viz., A, T, C and G (representing 4-amino
acids). However, 1000 of the aforesaid four
bases, the number usually contained in an average gene, may be conveniently
arranged upto 41000 different variants. Therefore, the
usual ‘genetic manipulation’ can be
accomplished successfully to provide all the ‘necessary vital informa-tions’ a cell essentially requires for
its growth and deliver its effective functions based on the astronomi-cal huge
number gene variants. In short, the ‘genetic
code’ overwhelmingly determines the intricacies of a nucleotide sequence for its conversion into the corresponding amino acid sequence of a particular
protein structure.
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