L26 - Mitosis and Microtubule Motors

Question 1

describe the 3 types of sindle microtubules - kinetichore,interpolar and astrial

Answer 1

Kinetichore:
attach to chromosome at kinetichore

interpolar:
overalp at cem]ntre of spindle = maintain structure

Astral = anchor spindle to cortex of cell

Question 2

describe dynamix instability of microtubules

Answer 2

continously grow and shrink

controlled by GTP cap regulated by microtubule-ascociated proteins (MAPs) and +TIPs –> EB1

Question 3

describe the motor proteins that organise and seperate chromosomes

Answer 3

Kinesisn -plus-end directed:
- Eg5/Kinesin-5 –> crosslinks and slides interpolation MTs appart –> spindle pole seperation

Dyneins - minus-end directed:
pull on astral MTs –> orient spindle and help move chromsomes to poles

Question 4

what is a contractile ring in cytokinesis

Answer 4

made of actin filaments + myosin-2 motors

= signals from spindle microtubules + RhoA GTPase pathway dirve formation

Question 5

describe the steps in cytokinesis

Answer 5

1. contractile ring forms at overlapping interpolar microtubule site
2. RhoA activation -> promote actin polymeristion + myosin-2 activation