Phases of the cell cycle; mitosis refresher,cytokinesis

Question 1

What happens during Interphase?

Answer 1

• 90% of a proliferating cell’s time
• Cell grows by producing proteins and organelles, copies its chromosomes, and prepares for cell division

Question 2

G1 (Gap 1)

Answer 2

Where most of a cell’s growth occurs.

Question 3

S (Synthesis)

Answer 3

DNA copied chromosomes attached at centromeres, still fully extended (not visible/condesation starts)

Question 4

G2 (Gap 2)

Answer 4

Cell completes preparations for Mitosis, chromosomes start to condense and spindle apparatus starts to form.

Question 5

M phase (Mitosis/Cytokinesis)

Answer 5

Subdivided according to state of chromosomes. Chromosomes finally condense enough to become visible at prophase.

Question 6

What are the 2 transient cytoskeletal structures that are required for cell division?

Answer 6

• Microtubules which are synthesized from tubulin protein during G2. This is needed to build the spindle to get through mitosis.
• Actin is involved in the division of the animal cell. Actin is often involved in contration.

Question 7

What is the effect of inhibition of tubulin polymerization?

Answer 7

Karyotype

Question 8

Cytokinesis in animal cells

Answer 8

Involves ring of actin filaments, under the plasma membrane, in association with motor proteins (myosin)

Question 9

Cytokinesis in plants

Answer 9

1. Anaphase: End of mitosis, where you start to pull the chromosomes apart. Microtubules and proteins define and organize the regions where new cell membrane and wall will form.
2. Telophase: Transport vesicles bud of the golgi and arrive carrying the components of a new cell wall.
3. Cytokinesis: Completed new cell wall.

Question 10

Stages of Mitosis 1

Answer 10

Before Mitsosis:
- Replicated chromosomes from S phase (still extended and not visible)
- Nuclear envelope is still intact

Mitosis Phase 1: Prophase
- Spindle formation is more developed
- Chromosomes are starting to condense

Prometaphase:
- In prometaphase nuclear envelope is broken down.
- Chromosmes are condensed
- Starting to attach the spindle fibres to organize and align these chromosomes and then eventually pull them apart

Question 11

Kinetochore

Answer 11

Where the kinetochore microtubules attach to the centromere. This attatchment is really important for proper allocation of chromosomes to the daughter cells.

Question 12

Stages of Mitosis 2

Answer 12

• Metaphase: Alignment of chromosomes on metaphase plate (equator of cell).