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Biology 1201A Study Guide - Midterm Guide: Sister Chromatids, Kinetochore, CentrosomePremium

3 pages120 viewsFall 2016

Course Code
Biology 1201A
Vera Tai
Study Guide

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Biology 1201 Test 1 Outcomes Part 4
Main features of each stage of mitosis with respect to cytoskeleton and chromatin
Chromatin is DNA and its structural proteins (histones) that it wraps itself around
Earlier in the cell cycle (G1), the chromatin is un-replicated and extends throughout the nucleus;
then after the S phase, that DNA is replicated and sister chromatids are formed which are
aligned tightly with each other with the help of cohesin
It is during the prophase where the chromatin is condensed into chromosomes that become
visible under the light microscope; during the prometaphase they are seldom visible as a double
structure but there are 2 sister chromatids attached at the centromere
It is during the metaphase where the chromosomes have completed their condensation and
have assumed their shape characteristic based on the location of the centromere and the
length and thickness of the chromatid arms
During anaphase, the chromatids separate and move to the opposite spindle poles
(kinetochores are the first sections of the chromosome to move towards the opposite poles)
In Telophase, the spindle dissembles and the chromosomes at each of the spindle poles de-
condense and return to the extended state that they were in during interphase
θ Cytoskeleton: contributes to the architecture and transport system of the cell
θ Each time a cell goes through division, the microtubule network is completely disassembled and
tubulin subunits are reassembled into a new struture alled spidle; durig G1, there is a
centrosome that contains a pair of centrioles and microtubules; and then after the S phase, the
pair of centrioles and the centrosome have doubled
θ Then during the prophase, the centrosome separates and starts moving to the opposite sides
of the cell; as this is happening, microtubules are forming spindles
θ Then in the prometaphase, the spindles enter the former nuclear area and the microtubules
from the opposite poles attach to the kinetochores of each chromosome
θ During the metaphase, the spindles line up the chromosomes and then in the anaphase,
cohesin is split between the sister chromatids and the motor proteins of the kinetochore pull
on the microtubule to reach the opposite poles; as the kinetochores pull themselves and the
sister chromatids towards the poles, the microtubules get dissembled
θ Telophase occurs where cytoplasm begins to furrow in the middle of the opposite poles and the
2 daughter cells are made with each having 1 centrosome
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