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 genomicor 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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