ADDITIONAL
INFORMATION
·
Barbara
Me Clintock (1951): Discovered jumping genes (segment of DNA
that can move from one place to another causing reshuffling of nucleotide sequences
in gene).
·
Hedges
and Jacob (1974): Named transposons to the jumping genes.
·
H.G.
Khurana et al (1968):Synthesised alanine
tRNA having 77 nucleotides (non-functional).
·
H.G.
Khurana et al (1979): Synthesised tyrosine tRNA having
207 nucleotides (functional).
·
Cornat
(1957): Discovered genomic
or genetic RNA.
·
R.J.
Roberts and P.A. Sharp (1977): Discovered split genes
(genes with introns) in eukaryotes, get Nobel Prize in 1993.
·
Benzer
(1962): Distinguished cistron,
recon and muton as three structural units of DNA. Other workers added the
terms replicon (unit of
replication), complon( unit of
complementation), Operon
(operational unit) and codon (a
sequence of three nucleotides specifying an amino acid).
·
Artificial
Gene: First artificial gene was synthesized by Khurana et al (1968). It was alanine
tRNA gene with 77 base pairs. The gene, however, did not function in living
system. Their second artificial and functional gene was tyrosine- tRNA gene with 207 base pairs (Khurana et
al.1979).
·
Satellite
DNA:
It is DNA with repetitive sequences which being heavier or lighter forms a
separate fraction during ultracentrifugation. Satellite DNA occurs in
heterochromatic regions as well as other parts.
·
Highly
Repetitive DNA: It consists of short simple sequences
which are repeated hundreds of thousands times (Skinner, 1978). Satellite DNA
is highly repetitive DNA, eg. pericentromeric regions of chromosomes.
Heterochromatic region of Y chromosome has special satellite DNA found only in
males.
·
Moderately
Repetitive DNA: They are repeated a few hundred times.
Centromere, telomere and the ends of transposons are moderately repetitive DNA.
·
DNA
Redundancy: Functional DNA is less than 1%. The
remaining is repetitive DNA, pseudogenes, repeated genes and introns.
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