By Brian GrossBy Brian Grossper2per2

Centrioles and AstersCentrioles and Asters

CentriolesCentrioles

Centrioles are barrel shaped organelles Centrioles are barrel shaped organelles found in the cells of most animalsfound in the cells of most animals

StructureStructureCentrioles are made of cylindrical microtubulesCentrioles are made of cylindrical microtubules There are nine triplets of these microtubulesThere are nine triplets of these microtubules They are arranged in a circle around the centerThey are arranged in a circle around the center Two are arranged in pairs that are at right angles from Two are arranged in pairs that are at right angles from

one another to form organelle called the centrosomeone another to form organelle called the centrosome

FunctionFunction

Centrioles play an Centrioles play an important function in cell important function in cell divisiondivisionThe centrosome is the The centrosome is the origin of all the cells origin of all the cells microtubulesmicrotubules Microtubules form Microtubules form

cytoskeleton of the cellcytoskeleton of the cell

Overview of Cell Division CycleOverview of Cell Division CycleGG2 2 of Interphaseof Interphase Centrosomes duplicate to form two pairs of centrioles, Centrosomes duplicate to form two pairs of centrioles,

the microtubules that extend from it are called the microtubules that extend from it are called astersastersProphaseProphase Chromatin in nucleus is more tightly coiled into Chromatin in nucleus is more tightly coiled into

chromosomes, spindles form between the chromosomes, spindles form between the centrosomes, which arrange themselves on opposite centrosomes, which arrange themselves on opposite “poles” of the cell“poles” of the cell

chromosome

Cell DivisionCell DivisionPrometaphasePrometaphase

Nuclear envelope breaks and the mitotic spindles growing from the Nuclear envelope breaks and the mitotic spindles growing from the centrioles move to center of cellcentrioles move to center of cell

Metaphase Metaphase Centrosomes arrange themselves on opposite sides of cell, Centrosomes arrange themselves on opposite sides of cell,

chromosomes create line on the imaginary equator of the cell, the chromosomes create line on the imaginary equator of the cell, the spindles attach to each other and to the center of the X shaped spindles attach to each other and to the center of the X shaped chromosome, called the centromerechromosome, called the centromere

Cell DivisionCell Division AnaphaseAnaphase

Sister chromatids (half of one chromosome) are pulled apart, move Sister chromatids (half of one chromosome) are pulled apart, move centromere first, poles move further apartcentromere first, poles move further apart

TelophaseTelophase The nuclear envelope begins to form in both daughter cells, The nuclear envelope begins to form in both daughter cells,

chromatids begin to unravel, the cells are pinched and separatedchromatids begin to unravel, the cells are pinched and separated

More FunctionsMore Functions

Centrioles are also important for the Centrioles are also important for the position of cilia and flagella in the cellposition of cilia and flagella in the cell When cells can’t use centrioles to create When cells can’t use centrioles to create

functioning cilia and flagella, it leads to functioning cilia and flagella, it leads to genetic disorders, ex. Meckel-Gruber genetic disorders, ex. Meckel-Gruber syndromesyndrome

OverviewOverview

Centrioles are made of nine triplets of microtubules Centrioles are made of nine triplets of microtubules arranged in a cylindrical shapearranged in a cylindrical shapeA pair of centrioles are centrosomes, from which the A pair of centrioles are centrosomes, from which the cells microtubules growcells microtubules grow Important for the cytoskeletonImportant for the cytoskeleton

During cell division, the centrioles duplicate and move to During cell division, the centrioles duplicate and move to opposite ends of the cell and are the origin of the opposite ends of the cell and are the origin of the microtubules that pull the chromatids apartmicrotubules that pull the chromatids apartAsters are radial microtubule arrays that are located Asters are radial microtubule arrays that are located around each pair of centriolesaround each pair of centrioles

sourcessources

http://http://en.wikipedia.org/wiki/Centriolesen.wikipedia.org/wiki/Centrioleshttp://www.gettyimages.com/Home.aspxhttp://www.gettyimages.com/Home.aspxhttp://www.cellsalive.com/cells/centriol.htmhttp://www.cellsalive.com/cells/centriol.htmCampbell-Reece Biology (textbook)Campbell-Reece Biology (textbook)