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XX-XY sex determination in plants
- 2. Melandrium album is a model dioecious plant species with an X/Y chromosome based sex determination system. Genotypical Male plants – AAXY Female plants – AAXX
- 3. Sometimes AAXY can be a hermaphrodite (all flowers are bisexual) or androhermaphrodite (forming both bisexual and male flowers on the same individual). Gametogenesis of X-Y happens in male meiosis The occurrence of bisexual flowers can be caused by mutation(deletion) of female suppressing gene on Y chromosome or as a consequence of a spontaneously, artificially induced change in DNA methylation patterns.
- 4. In Melandrium album , Y chromosome plays an important role in sex determination as it contains female suppressing gene and male determining gene responsible for mature anther development. Y chromosome is longer than X chromosome and they form a heteromorphic bivalent at meiosis.
- 5. X and Y chromosome have common segment IV, which helps in pairing and regular disjunction of X and Y chromosomes during meiosis. The remainder of Y chromosome has 3 segments namely, Segment I – Supresses femaleness Segment II - initiates anther development Segment III- controls late stage of anther development
- 6. X chromosome has a differential segment V, which promotes femaleness in the absence of female suppressing segment I on Y chromosome. 2A+XX 1.00 female 2A+XY 0.5 male 2A+XXY 1.00 female 3A+XXY 0.67 male (occasional) 4A+XXY 0.5 male 4A+XY 0.25 male (occasional) 4A+XXXY 0.75 male (occasional) 4A+XXXXY 1.00 hermaphrodite