BIO330H5 Lecture Notes - Lecture 5: Endosperm, Double Fertilization, Polyploid
Document Summary
Diploids - how it"s supposed to work: 2n (same species parents) -> n (gametes) -> 2n f1 generation. Autopolyploid = multiply set from same species: 2n (same species parents) -> 2n (gametes) -> 4n f1, diploid gamete instead of haploid. In most cases, it won"t develop normally: but occasionally, the tetraploid can survive and behave functional, ultimately, most tetraploids undergo diploidization (gradually turning back into diploid) Tetraploids cannot mate with parents again, successfully: reproductively isolated from parents = more chromosomes, mispairing, crossing over make it worse, polyploidy can lead to speciation. Sexual reproduction is where variation comes from (generate new genets) Most plants are capable of sexually reproduce. Double fertilization: one pollen nuclei fertilizes egg nucleus, generating a new embryo (diploid, the other combines with 2 or more endosperm nuclei to produce polypoid nutritive tissue. Endosperm is a genetic dead end = cannot get another polypoid. Without double fertilization, there is no endosperm.
