花粉粒核分裂前期における減数分裂螺旋の解撚

抄録

The relational twists of chromonemata in prophase of pollen mitosis originate from the major spirals in meiotic second anaphase. The major spirals elongate longitudinally during the resting stage. Therefore, every gyre of major spirals give rise to two relational twists in prophase of the pollen mitosis. There were observed as many as 17 twists in an arm of chromosome A, which shows only 11 major spirals at meiosis. This is one of the evidences supporting the above conclusion that the relational twists result from the meiotic major spirals. The number of twists decreases to none until metaphase. Modes of unravelling of the twists were classified into 5 types according to the positions where unravelling takes place. The first type comprises chromonemata showing unravelling, which covers evenly throughout the whole arm length. The second, third, forth and fifth represent the types of unravelling which happen in precedence at distal end, kinetochore region, middle portion, and both distal and kinetochore region respectively.