What is terminalization of chiasma
Answers
Answer:
On the basis of my own and published data, a conclusion was made that meiotic terminalization of chiasmata, which was postulated by Darlington, does not occur. The chiasmata remain in the sites where they appear, until the disjunction of homologous chromosomes in meiotic anaphase I. The disjunction of homologues is accounted for by repulsion of the sister chromatids.
Explanation:
In maize microsporocytes Heterozygous for a chromosome 2 interchange chromosome (which carries a homoeologous Tripsacum chromosome segment substituted for the distal half of its short arm), normal synapsis usually occurs at pachytene throughout the bivalent, but crossing over is almost entirely restricted to the homologous proximal region of the arm, (where it apprently occurs frequently). At diakinesis chiasmata were very often found to be located immediately proximal to an easily observable terminal knob of the Tripscacum chromosome segment. It was concluded that chiasmata, initiated in the homologous proximal region, had been maintained while terminalizing across the homoeologous region. It was also noted that heterozygosity for a telomere (and distal region) foreign to maize does not seem to inhibit pairing effective for crossing over in the homologous proximal portion of the chromosome arm.