The two concepts give slightly more levels regarding anaphase separa- tion
The latest Family members from Mitosis and you can Meiosis (centered on Darlington). Keep in mind that new chromosomes is actually twice at the their basic looks in mitosis, but not regarding basic (leptotene) phase out-of meiotic prophase. It few in zygotene, begin to end up being double (split) in the pachytene, and are also double over the last amounts from meiotic prophase (diplotene and you may diakinesis). Within the mitosis anaphase begins because of the section of your centromeres, however in meiosis it doesn’t are present till the anaphase away from the second division (not shown). Darlington try the first to ever recommend that in case your parasynaptic interpre- tation is adopted, every differences when considering meiosis and you will mitosis normally, with the help of not too many hypotheses, end up being deduced regarding brand spanking new difference in the fresh new singleness otherwise doubleness of prophase posts.
The guy advised one to homologous chromosomes, or in other words homologous chromonemata, focus each other into the pairs. Which attraction are came across within the mitotic prophase, however during the early meiotic prophase, the spot where the chromosomes reaches earliest unmarried, and certainly will simply fulfill the attraction because of the upcoming with her inside zygotene combining. In the meiosis, the latest spHtting of chromosomes, and that takes place in the newest interphase before a mitotic section, doesn’t happen right until pachytene when the chromosomes are actually relevant inside pairs. It for this reason supplies a collection of five relevant posts and these fall apart to your diplotene loops, being held with her from the change out-of lover from the chiasmata. The brand new dropping aside of four posts is evidence you to in the event a couple of homologous chromosomes desire each other, one collection of homologous chromonemata repels another equivalent few.
Ergo Darlington supposed that the spUtting off a beneficial chromosome when preparing for the next mitotic office happens in this new interphase just before one division, and that this new singleness of your meiotic chromo- somes is born just to the point that it begin condensation and you can con- grip toward department till the busting features occurred. This hypo- thesis is named this new Precocity Idea. A change in the easy precocity concept might have been suggested by Huskins,^ who accepts Darhngton’s hypotheses the differences when considering the 2 sorts from section are caused by the repulsion ranging from sets off chromonemata and you will interest ranging from single chromonemata, however, denies Darlington’s account of your source of the singleness off this new meiotic chromosomes for the prophase. Based on Huskins, the splitting of your own chromosomes for 1 section happen throughout the prior division, developing a so-called tertiary split up that causes the newest chromo- some pairs during the mitotic metaphase as in fact quadripartite, those in the meiotic metaphase octopartite government.
The Mechanics Of the CHROMOSOMES II5 proof to get telosynapsis was adduced regarding occurrence out-of continued bands away from chromosomes during the meiotic metaphase in some organisms (mainly Oenothera), but several other much more satisfactory explana- tion can now be provided with because of it (p
During the interphase ahead of meiosis, which tertiary spUt need to be supposed to be lost in a few means, merely to getting restored within pachytene; within new diakinesis phase it ^ Cf. Huskins and you will Smith 1934. Il6 An overview of Modern Genes is succeeded by various other separated into the office which observe the next meiotic section. Based on Darlington, the first separation of your chromo- somes into the anaphase is actually mitosis considering the section off the fresh new centromeres during this period plus meiosis in order to a greater repulsion between your https://datingranking.net/cs/bdsm-recenze/ centromeres which today begins to overcome this new forces carrying this new chromosomes along with her in the chiasmata. Based on Huskins, at exactly the same time, the fresh break up of one’s mitotic chromosomes is analogous on the creation away from diplotene loops ; it is a result of the formation of new tertiary split and that converts the matched mitotic chromosomes toward a set of collectively repelling matched up posts.