The organization of microtubules (MTs) in the mitotic spindle apparatus has been shown to involve a combination of centrosomal-based nucleation and hypothesized to involve acentrosomal branching MT nucleation. Here, Petry et al. (2013) uses Xenopus egg extracts to successfully observe branching MT nucleation from existing microtubules utilizing total internal reflection microscopy (TIRF). Direct observation of branching MT nucleation highlighted both the activating effect of RanQ69L and its effector protein TPX2 on branching MT nucleation, and the polarity conservation of daughter MTs. Testing for required molecular factors using immunodepletion, it was shown that the γ-tubulin ring complex (γ-TuRC) is required for primary nucleation while the protein complex augmin is required for branching. Furthermore, components of the RanGTP signaling pathway are shown to induce observed branching MT nucleation. The results by Petry et al clearly demonstrate branching MT nucleation and is a significant achievement, being the first ever visualized in a metazoan system. Further research should focus on deciphering the mechanistic interactions between that RanGTP and TPX2, specifically its C-terminus CT-TPX2, that stimulate MT nucleation. In addition, even though augmin has been shown to play a key role in spindle morphogenesis through branched MT nucleation, its relationship with other molecular factors should be further elucidated.
Background
Mitosis and meiosis are key cellular
[4] – Frank Schluenzen et al, Structure of Functionally Active Small Ribosomal Subunit at 3.3A Resolution
Chromosome pairs line up across the equator of the spindle at metaphase I (5). In anaphase I the chromosomes separate and travel to opposite ends of the spindle. The chromosomes migrate to the equators of two new spindles for metaphase 2 (7). Next the chromatids are pulled apart in anaphase 2 to form four clusters of chromosomes in telophase 2. The nuclear envelopes reform around four haploid nuclei that will give rise gamete
2) Why are onion root tip and whitefish blastula areas that are ideal to view mitosis?
Out of a total from 26 sequences only 6 were made up of 4‘s while 20 were composed of different structures of 2‘s. This tells us that 77% of the asci showed crossing over while 23% did not.
In the onion root tip, regions other than the apical (or at top of) meristem contain cells that are not actively dividing. These cells are in interphase. In this case, they would represent the majority because cells spend most of their time in interphase anyway. They are elongating, differentiating, and performing their functions for the organism. Mitotic stages would not have been found in these areas.
Without cell division and the cell cycle nearly all life would fail to exist. Cell division allows an organism to not only replace its own cells but to create offspring. The cell cycle consists of two main parts: interphase and mitotic phase. Within these two phases the processes can be broken down into further categories. Interphase can be broken down into three subphases that are the necessary preparations the cell makes in order to be ready to divide during mitosis. For this lab we looked mainly at the mitotic phase because of its fascinating and rapid changes to the cell. The cell types we looked at were prepared slides of whitefish and onion root tip.
D. The kinetichore is the site of attachment of the centromere to the nuclear spindle apparatus.
18) Looking into your microscope, you spot an unusual cell. Instead of the typical rounded cell shape, the cell has a very narrow middle separating two bulging ends. It sort of looks like the number 8! Then you realize that this cell is
[A labelled diagram of Metaphase here, and put a note next to it saying "Note
To observe mitosis in onion root tip cells and record the different phases of mitosis.
P1 – Describe the microstructure of a typical animal cell and the functions of the main cell components. A typical animal cell is seen as a tiny, three dimensional sac which is in fact made up of many components, each as important as the other. The microstructure of an animal cell was in fact uncovered mainly through the use of both cell fractionation and electron microscopy. Each main component has its own, individual function which helps a cell to function and maintains the cell membrane. The components that I will be describing include the cell membrane, nucleus, cytoplasm, mitochondria, lysosomes, Golgi bodies, centrioles, endoplasmic reticulum (both smooth and rough) and ribosomes.
From the above article I would say that microcelebreties have become very popular now-a-days with the help of the social media, they launch themselves as a celebrity with their own equity just like a brand. While going through Instafame documentary of Shawn Megira, there was a girl named Niana Guerrero who was 11 years old, she also got very famous on instagram by her dance moves. Now, she got almost 1.9 million followers in instagram, just with her dance videos. Microcelebrity is a kind of communication, a “way of thinking of themselves as a celebrity, and treating others accordigly” (Marwick, 2013a, p. 115). The temporality of microcelebrity focuses of what constitutes contemporary procedures of celebrification, to a larger extent, includes
Yes, we could locate the various stages of mitosis. The prophase, metaphase, anaphase, and telophase stages were clearly present in the cells.
Bettelheim, Brown, Campbell and Farrell assert that polypeptide chains do not extend in straight lines but rather they fold in various ways and give rise to a large number of three-dimensional structures (594). This folding or conformation of amino acids in the localized regions of the polypeptide chains defines the secondary structure of proteins. The main force responsible for the secondary structure is the non-covalent
Overexpression of the HEPN domain in HeLa cells following three hours of starvation indicates that sacsin plays a key role in lysosomal transport due to the reduced efficiency of perinuclear lysosomal clustering. HEPN’s property of dimerizing may be disrupting the function of with full-length sacsin by preventing endogenous sacsin from dimerizing within the cell. Thus, dimerization may be essential to sacsin’s function, particularly for binding JIP3, which is necessary for lysosomal transport7. HATPase 3 overexpression may be occupying JIP3 binding, but was not found to disrupt lysosomal localization following starvation, perhaps due to the truncated size of this deletion construct.