Scientists from the Centre for Cellular and Molecular
Biology (CCMB) found that all that non-coding part is not junk. While more than
50 per cent of the non-coding DNA was repetitive, simple sequence repeats
(SSRs) account for about three per cent of the human genome.
Large percentage of organism’s genome size is noncoding
DNA, the proportion of coding versus noncoding DNA varies greatly.
Junk DNA is a term for the portions of a genome sequence
for which no discernible function has been identified. This term was introduced
in 1972.
Each human has 100 billion km of total
DNA, enough to reach sun and come back 300 times. But of the 3.3 billion
nucleotides of human genome, less than two per cent code for proteins while the
remaining 98 per cent is non-coding in nature and generally described as “junk
DNA”.
Vast majority of the genome is made up of
DNA that doesn't seem to contain genes or turn genes on or off.
Accumulation of non-coding part of the
genome appears to be the driving force behind the evolution of complexity in
living organisms which indicates the biological complexity had not evolved by
the addition of more genes to the genome but by more sophisticated regulation
of the pre-existing genes.
Dr. Rakesh Mishra pointed out that SSRs,
including GATA repeats were known to show polymorphisms-small size variations
in size of the repeat at different loci in the genome within a population. Such
variations were the basis of DNA finger printing that could establish the
genetic identity of a person.