Date of publication: 2017-08-30 15:16
Both the assembly and the function of the mitotic spindle depend on microtubule -dependent motor proteins. As discussed in Chapter 66, these proteins belong to two families x57569 the kinesin -related proteins , which usually move toward the plus end of microtubules, and the dyneins , which move toward the minus end. In the mitotic spindle, the motor proteins operate at or near the ends of the microtubules. These ends are not only sites of microtubule assembly and disassembly they are also sites of force production. The assembly and dynamics of the mitotic spindle rely on the shifting balance between opposing plus-end-directed and minus-end-directed motor proteins.
Population Systems and Mutualism Extra Credit Article Review
First Comes Global Warming and Then an Evolutionary Explosion
Effect of Environmental Toxins on Wildlife- Wildlife Forensics
Algae making Biofuel
Algae and Animals living together: Going Green (endosymbiosis and mutualism)
The attachment of the chromosomes to the spindle is a dynamic process. When viewed by video microscopy, it seems to involve a x5756c search and capture x5756d mechanism, in which microtubules nucleated from each of the rapidly separating centrosomes grow outward toward the chromosomes. Microtubules that attach to a chromosome become stabilized, so that they no longer undergo catastrophes. They eventually end up attached end-on at the kinetochore , a complex protein machine that assembles onto the highly condensed DNA at the centromere (discussed in Chapter 9) during late prophase. The end-on attachment to the kinetochore is through the plus end of the microtubule , which is now called a kinetochore microtubule ( Figure 68-66 ).
The mitotic spindle begins to self-assemble in the cytoplasm during prophase. In animal cells, each of the replicated centrosomes nucleates its own array of microtubules, and the two sets of microtubules interact to form the mitotic spindle. We see later that the self-assembly process depends on a balance between opposing forces that originate within the spindle itself and are generated by motor proteins associated with the spindle microtubules.
56 - Diffusion & Osmosis
57 - Enzyme Catalysis
58 - Mitosis & Meiosis
59 - Plant Pigments & Photosynthesis
55 - Cellular Respiration
56 - Molecular Biology
57 - Genetics of Drosophila
58 - Population Genetics & Evolution
59 - Transpiration
65 - Circulatory System Physiology
66 - Animal Behavior
67 - Dissolved Oxygen
The AP Chemistry Page hosts the resources for the class, which include PowerPoints in HTML 5 format, notes, and review activities. I am continually making modifications to these resources to align with the College Board's AP Chemistry Framework. Though I developed the resources for my AP students, they will probably also prove useful to college students taking a first year chemistry course.
Genes are lengths of DNA that code for proteins and are the basic units of heredity. Different types of the same gene are called alleles and are responsible for variation in inherited traits. Each gene can be mapped to a specific location on a chromosome, and the proximity of different genes determines their linkage, or the likelihood that they will be inherited together. Recombination is more likely to separate alleles that are further apart on a chromosome than those with little space for crossovers between them.
At least that s the way it usually happens. In rare cases, an XX individual becomes a male or an XY individual becomes female. Researchers realized that studying the genes of these sex-reversed people could lead them to the master switch for sex determination. They subsequently identified a gene called SRY (sex-determining region on the Y chromosome).