Week 9 - Cell division (mitosis)

Question 1

What are the 6 main stages in mitosis

Answer 1

1. Interphase
   Prophase
   Prometaphase
   Metaphase
   Anaphase
   Telophase

Question 2

mnemonic for remembering the stages of mitosis

Answer 2

Please Pee on the MAT

Question 3

What is the interphase stage

Answer 3

The phase preceding mitosis where the cell prepares for division.
- 2 centrosomes have formed
- Chromosomes, duplicated during S phase, have not yet condensed

Question 4

What happens in prophase

Answer 4

Marks the beginning of mitosis. During this stage the chromatin condenses into visible chromosome.
- Chromosome Condensation: The chromosomes are starting to condense into discrete chromosomes made out of 2 sister chromatids each with a ‘central’ centromere
- Spindle Formation: The mitotic spindles are starting to form and extend from the asters located at opposite ends of the cell. The spindle fibers will help separate the sister chromatids later in mitosis

Question 5

What happens in prometaphase

Answer 5

Prometaphase is a transitional stage between prophase and metaphase. During this stage, the spindle fibers attach to the kinetochores, which are protein structure located at the centromeres of the chromosomes.
-nucleur membrane breaks
- Chromosome attachment: Microtubules start to bind to the kinetochore and start jerking the chromosomes back and forward

Question 6

What happens in metaphase

Answer 6

In metaphase the chromosomes align along the cell’s equatorial plane (the metaphase plate). This alignment ensure that each daughter cell will receive an equal number of chromosomes during division.
- Chromosome alignment: The chromosomes convene along the metaphase plate in a single plane
- The chromosomes are now attached to a centrosome at opposite ends of the spindle

Question 7

What happens in anaphase

Answer 7

Anaphase is the stage during which the sister chromatids separate and move towards opposite poles of the cell.

• Sister chromatid separation: The cohesion proteins binding the 2 daughter chromosomes are cleaved allowing them to move independently towards opposite spindle poles
• Chromosome movement: The 2 daughter chromosomes begin moving towards opposite ends of the cell pulled from the kinetochore - where each pole recives an equal and complete set of chromosomes

Question 8

What happens in telophase

Answer 8

Telophase marks the end of chromosome movement and the beginning of cytokinesis, the division of the cytoplasm.

• Chromosome Decondensation: 2 daughter nuclei form in the cell as the chromosomes become less condensed returning to their extended chromatin state.
• New nuclie for around the chromasomes
• Cytokinesis: cytokinesis divides the cytoplasm and organelles between the 2 daughter cells

Question 9

What are the steps in binary fission

Answer 9

1.The genetic material (DNA) is replicated
2. Bacteria elongates and the genetic material and organelles move to other sides of the cell
3. A new cell wall forms down the middle of the bacteria cell
4. Two daughter cells pull apart

Question 10

What are the differences between mitosis and meiosis

Answer 10

Meiosis produces cells for sexually reproducing organisms (gametes = sperm and egg cells) , where as mitosis produce cells for growth, repair, and asexual reproduction in multicellular organisms

Meiosis produces daughter cells with half the number of chromosomes as the parent cell - where as mitosis produces the full 46 chromosomes

Meiosis involves 2 rounds of cell division producing 4 daughter cells where as mitosis only divides once

meiosis generates different genetic combination where as mitosis produce genetically identical daughter cells