BIO 121 Lecture Notes - Lecture 5: Spindle Apparatus, Sister Chromatids, Nuclear Membrane
Document Summary
Chromosomes condense by wrapping around proteins and become visible sister chromatids. Nuclear envelope and nucleolus breaks down: prometaphase. Kinetochores (proteins) appear at the centromeres . Mitotic spindle microtubules (the vertical lines aka spindle fibers) attach to kinetochores . By the end of this phase, all of the kinetochores are attached to microtubules: metaphase. Mitotic spindle is fully developed, centrosomes are at opposite poles of the cell. Chromosomes are lined up at the metaphase plate ( center) Each sister chromatid is attached to a spindle fiber originating from opposite poles: anaphase. Cohesin proteins binding the sister chromatids together break down . Non-kinetochore spindle fibers lengthen, elongating the cell. Sister chromatids (now called chromosomes) are pulled toward opposite poles : telophase. Chromosomes arrive at opposite poles and begin to decondense . Nuclear envelope material surrounds each set of chromosomes . In animal cells: a ring of actin filaments forms at the metaphase plate.
