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COURSE Principles of inheritance and variations Lesson 14 Complimentary genes Dr. Praveen Kumar Agrawal M.Sc., Ph.D., CSIR NET (JRF). SRF, GATE 21Years of Pre-medical teaching experience
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COMPLEMENTARY GENES Complementary genes are two pairs of non-allelic genes (present on separate loci), which together produce a phenotypic character. Dominant alleles (atleast one) of both genes is required for the expression of the character i.e., the character would appear only if the dominant alleles of both the genes are present. It means both genes are complementary to each other. For example, in 'sweet pea' (Lathyrus odoratus), the pink colour of flower depends upon the presence of two pairs of non-allelic genes. The pink colour appears only when the dominant alleles of both genes are present. If dominant allele of any one gene is missing, colour does not appear and white flower is produced.
Pure pinlk PPSS ppss Pure white PSPS ps ps F1 PpSs Pps PpSs All individuals are pink
Selfing of F1 PpSs PpSs Male Female PS PPSS Pink ps ps PPSs PpSS Pink PpSs PS Pink Pink PPSs PPss PpSs Pink Ppss White Pink White PpSS PpSs ppSS ppSs ps Pink Pink White White PpSs Ppss White ppSs White ppss White ps Pink
Results Phenotypic ratio 9:7 (Pink 9, White 7) It is clear from the above figure, that for the appearance of pink flower, the dominant alleles of both genes are necessary. Thus, both genes are complementary to each other. None of these can alone produce the character.
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