Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.) Filing date Publication date Priority to US41878502P priority Critical Priority to US10/682,689 priority patent/US7552605B2/en Application filed by Seton Co filed Critical Seton Co Priority to US12/360,862 priority patent/US20090130429A1/en Assigned to SETON COMPANY reassignment SETON COMPANY ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Original Assignee Seton Co Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.) Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.) Abandoned Application number US12/360,862 Inventor Hermann Winkler Current Assignee (The listed assignees may be inaccurate.
Vickers m41 photoplan microscope pdf#
It is suggested, therefore, that chromosomes at maximum preleptotene condensation cannot enter a meiotic sequence without first undergoing a within-chromosomal reorganization of their chromatin, and that preleptotene chromosome decondensation stage represents such a reorganization.- Google Patents US20090130429A1 - Natural Grain LeatherÄownload PDF Info Publication number US20090130429A1 US20090130429A1 US12/360,862 US36086209A US2009130429A1 US 20090130429 A1 US20090130429 A1 US 20090130429A1 US 36086209 A US36086209 A US 36086209A US 2009130429 A1 US2009130429 A1 US 2009130429A1 Authority US United States Prior art keywords leather base coat hides coating nappa Prior art date Legal status (The legal status is an assumption and is not a legal conclusion. Two parallel threads (chromatids) are visible in chromosomes at preleptotene condensation stage while, in chromosomes at leptotene, invariably only a single thread is seen. It is concluded that preleptotene chromosome condensation stage has no effect on normal meiotic chromosome pairing behaviour and probably has no significant function. In 'Black Beauty', however, the control regulating the initiation of meiosis apparently is effective later in the cell cycle and acts only after p.m.cs have entered mitotic prophase. In normal Lilium genotypes meiosis is initiated by p.m.cs at G2 of premeiotic interphase. It is suggested, therefore, that preleptotene condensation and decondensation represent a true mitotic reversion in which metaphase and anaphase are omitted. Similarly, the appearance and behaviour of chromosomes at preleptotene decondensation is indistinguishable from that normally seen at mitotic telophase. The appearance and behaviour of chromosomes at preleptotene condensation stage is the same as that displayed by chromosomes at mitotic prophase. The nature and possible significance of preleptotene chromosome condensation and decondensation are discussed. Thereafter chromosomes underwent decondensation and elongation and eventually passed into leptotene without first entering any other stage. At this stage the appearance of the chromosomes was indistinguishable from that of late prophase or prometaphase chromosomes at mitosis. At maximum chromosome contraction the diploid chromosome number (2n = 24) could often be counted, but no evidence of association of chromosomes was seen. All the p.m.cs within an anther loculus underwent preleptotene chromosome condensation stage with a degree of synchrony not less than that found at early first meiotic prophase. 'Black Beauty' p.m.cs entered preleptotene chromosome condensation stage from G2 of premeiotic interphase having completed DNA synthesis. A brief illustrated description is given of the appearance of p.m.cs at various stages of preleptotene chromosome condensation in both methylene blue stained anther sections, and in Feulgen stained anther squashes. chromosomes during preleptotene condensation and decondensation was essentially the same as that described by Walters (1970, 1972) for the corresponding stages in Lilium longiflorum cv. Moreover, the preleptotene condensation and decondensation stage was apparently shorter in e.m.cs (about 0.7 days) than in p.m.cs. However, the maximum degree of chromosome contraction at the preleptotene condensation stage was much greater in p.m.cs than in e.m.cs. Preleptotene chromosome condensation and contraction also occurred in embryo sac mother cells (e.m.cs) of 'Black Beauty'. The duration of this period was estimated to be about 1.16 days in pollen mother cells (p.m.cs) of plants grown at 20 degrees C. A period of chromosome condensation followed by decondensation occurs between premeiotic interphase and leptotene in Lilium hybrid cv.