In 1940s, Beadle and Tatum proposed one-gene-one protein hypothesis which explains that one gene encodes for one protein. However, if one gene consists of 1,500 base pairs, a protein of 500 amino acids in length would be synthesized. In addition, if the same sequence read in two different ways, two different amino acids would be synthesized by the same sequence of base pairs. It means, the same DNA sequence can synthesize more than one proteins at different time. It was realized for the first time when the total number of proteins synthesized by X174 exceeded from the coding potential of the phage genome. A similar phonemenon is found in the tumour virus SV40 where the total molecular weight of proteins (i.e. VP1, VP2 and VP3) synthesized by SV40 genes is much more than the size of the DNA molecule (5200 base pairs i.e. 1,733 codons). From this observations the concept of overlapping genes has emerged.
OVERLAPPING GENES (GENES WITHIN GENES)
In 1940s, Beadle and Tatum proposed one-gene-one protein hypothesis which explains that one gene encodes for one protein. However, if one gene consists of 1,500 base pairs, a protein of 500 amino acids in length would be synthesized. In addition, if the same sequence read in two different ways, two different amino acids would be synthesized by the same sequence of base pairs. It means, the same DNA sequence can synthesize more than one proteins at different time. It was realized for the first time when the total number of proteins synthesized by X174 exceeded from the coding potential of the phage genome. A similar phonemenon is found in the tumour virus SV40 where the total molecular weight of proteins (i.e. VP1, VP2 and VP3) synthesized by SV40 genes is much more than the size of the DNA molecule (5200 base pairs i.e. 1,733 codons). From this observations the concept of overlapping genes has emerged.
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