Practice question

Genetic or nuclear male sterility governed by genes residing in nucleus designated ms or gms genes, often recessive requiring homozygous state to express sterility. Inheritance follows Mendelian segregation. Molecular basis involves transcription factors regulating tapetal development such as bHLH factor AMS in Arabidopsis, MYB80 and MS1 MMD1. Loss-of-function mutations cause tapetum persistence, failure providing nutrients and sporopollenin precursors to microspores leading to abortion at vacuolate stage. Because causative genes nuclear, referred also as genic or nuclear sterility, distinct from cytoplasmic inheritance. Maintenance requires crossing heterozygous fertile sister with sterile plant producing one sterile to one fertile ratio, enabling propagation. Disadvantage need to rogue fertile progeny during A-line multiplication increasing labor but advantage stability independent of environment unlike EGMS. This understanding supports competitive exam preparation for NEET, GATE and CSIR NET concepts linking genotype with phenotype through molecular pathways involving transcription factors, hormones and metabolic enzymes that regulate development, adaptation and reproductive biology in applied breeding programs.