In the mitosis anaphase starts from the department of the centromeres, however in meiosis this does not can be found before the anaphase of the following division (perhaps not found)
This new Family members away from Mitosis and you will Meiosis (according to Darlington). Observe that the newest chromosomes was twice at the the earliest physical appearance into the mitosis, yet not throughout the first (leptotene) stage off meiotic prophase. It few from inside the zygotene, start to getting double (split) from inside the pachytene, consequently they are twice in the last stages of meiotic prophase (diplotene and you may diakinesis). This new Aspects Of your own CHROMOSOMES II5 evidence in support of telosynapsis is adduced regarding the occurrence from continued groups of chromosomes from the meiotic metaphase in a number of bacteria (chiefly Oenothera), but several other even more satisfactory explana- tion can now be given for it (p. Darlington are the first to advise that should your parasynaptic interpre- tation try used, all the differences when considering meiosis and mitosis can be, with the help of not too many hypotheses, become deduced on the unique difference between the new singleness or doubleness of your own prophase posts.
He advised that homologous chromosomes, or rather homologous chromonemata, interest each other for the pairs. So it destination was came across inside mitotic prophase, yet not at the beginning of meiotic prophase, where the chromosomes reaches earliest solitary, and will just fulfill the destination of the upcoming with her inside the zygotene pairing. Inside meiosis, the new spHtting of the chromosomes, and this happens in the latest interphase in advance of an effective mitotic section, doesn’t happens till pachytene if the chromosomes seem to be related in the sets. It thus produces some five associated threads and these break apart with the diplotene loops, are held together by the change regarding spouse at the chiasmata.
Therefore Darlington heading the spUtting from an effective chromosome when preparing for another mitotic division takes place in the fresh interphase just before you to definitely division, which brand new singleness of your meiotic chromo- somes arrives in order to the truth that they initiate condensation and you may scam- traction towards the office up until the splitting features occurred. It hypo- thesis is named this new Precocity Principle. A modification of the simple precocity concept could have been advised because of the Huskins,^ whom allows Darhngton’s hypotheses the differences between the 2 kinds out-of division are due to brand new repulsion anywhere between pairs of chromonemata and you may attraction ranging from unmarried chromonemata, however, rejects Darlington’s account of source of one’s singleness off brand new meiotic chromosomes into the prophase. Centered on Huskins, the brand new breaking of the chromosomes for starters section happen during the the last division, forming a thus-titled tertiary separated that causes the new chromo- some pairs on mitotic metaphase to get in fact quadripartite, those people during the meiotic metaphase octopartite authorities.
Brand new dropping apart of your own five threads is research you to even if a couple of homologous chromosomes attract one another, one to group of homologous chromonemata repels several other similar few
When you look at the interphase just before meiosis, so it tertiary spUt have to be supposed to be missing in a number of ways, simply to feel restored at the pachytene; within the latest diakinesis stage it ^ Cf. Huskins and you will Smith 1934. Il6 An overview of Progressive Genes try succeeded because of the other separated for the section which uses the following meiotic department. The two theories bring a bit other membership away from anaphase separa- tion. Based on Darlington, the initial break up of your own chromo- somes from inside the anaphase is in mitosis because of the office of the new centromeres at this stage as well as in meiosis so you can an increased repulsion between your centromeres which today whiplr mobile begins to beat the new forces holding the brand new chromosomes along with her at the chiasmata. Predicated on Huskins, at exactly the same time, the latest break up of your own mitotic chromosomes try analogous with the development out of diplotene loops ; it’s a result of the formation of the tertiary split which turns the coordinated mitotic chromosomes on the a couple of mutually repelling paired threads.
