Class Notes (839,430)
Canada (511,348)
Biology (2,437)
Lecture

Mechanics of Cell Division

3 Pages
91 Views

Department
Biology
Course Code
BIOLOGY 2D03
Professor
Laura Parker

This preview shows page 1. Sign up to view the full 3 pages of the document.
Description
Mechanics of Cell Division Mitosis and Cytokinesis • Interphase  DNA is replicated (S phase) • G1 and G2 phases  cell growth • M phase  nuclear division (mitosis) and cell division (cytokinesis) M Phase • Chromosome condensation • Then specialized cytoskeletal machines pull the chromosomes apart (mitotic spindle) • Finally the cell is split in half (contractile ring) Chromosome condensation • Sister chromatids bound tightly together by protein complexes called cohesions after replication in S phase • Cohesions are deposited along the length of each chromatid and are broken only late in mitosis • At the onset of mitosis  chromosomes compacted and become 50x shorter o Condensins mediate this process  use ATP hydrolysis to drive the DNA compaction rxn M Phase depends upon the duplication of centrosomes in the preceding interphase • Centrosomes  microtubule organizing center (MTOC), nucleate the growth of microtubules o Contain a fibrous centrosome matrix containing a pair of centrioles (which contain about 50 copies of γ-tubulin ring complex) o The process of centrosome duplication and separation is called the centrosome cycle o As mitotosis begins, the 2 centrosomes split apart and move to opposite ends of the nucleus o Each centrosome (pair of centrioles) nucleates a radial array of microtubules called an aster, which will become the two poles of the mitotic spindle 5 stages of mitosis • Prophase  sister chromatids condense, and mitotic spindle begins to assemble outside the nucleus • Prometaphase  nuclear envelope breaks down (in mammals) • Metaphase  chromosomes are aligned at the equator of the spindle, medway between the spindle poles. Kinetochore microtubules attach sister chromatids to opposiute spindle poles • Anaphase  sister chromatids synchronously separate and the daughter chromosomes move towards the spindle poles. Kinetochore microtubules get shorter and spindle poles move outward • Telophase  the daughter chromosomes arrive at the two poles, and a new nuclear envelope assembles around each set. Mitotic spindle • Segregates replicated chromosomes • Constructed of microtubules and associated proteins • 3 classes of microtubules play a role: o astral microtubules o kinetochore microtubules o overlap microtubules • kinesins and dyneins also mediate the assembly and fxn of the spindle Processes that mediate the formation and function of the spindle • Microtubule instability increases at M phase o The relatively few, long microtubules radiating out from centrosome convert to larger number of shorter, more dynamic microtubules. o Increasing the amount and/or activity of catastrophins (and decreasing MAPs) destabilizes microtubules by increasing dynamic instability • Actions of opposing motor proteins halp set up the spindle by arranging and moving microtubules • Kinetochores attach chromosomes to microtubules  search and capture mechanism o Microtubu
More Less
Unlock Document

Only page 1 are available for preview. Some parts have been intentionally blurred.

Unlock Document
You're Reading a Preview

Unlock to view full version

Unlock Document

Log In


OR

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


OR

By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.


Submit