Mitosis - The Mechanics

Question 1

Difference between mitosis + meiosis - Cell produces

Answer 1

Mi - 2 diploid cells that are genetically identical

Me - 4 haploid cells that are genetically identical

Question 2

Process of mitosis

Answer 2

Starts w/ 2n in interphase
- Replicated to form sister chromatids in prophase
- Lines up along equator - anaphase
- Each homologous pair pulls to each pole - telophase
Results in 2 identical daughter cells

Question 3

Process of Meiosis s

Answer 3

Starts quite similarly BUT
- homologous chromosomes are separated
- Then in PMAT II the sister chromatids are pulled apart

Question 4

Cohesin

Answer 4

Protein complex to stick chromosomes together
- Has a ‘hinge’ that can be locked or unlocked - holds sister chromatids together

• Multiple subunits that form a ring
• Keeps products of replication together
• Broken open at anaphase checkpoint

Question 5

SMC

Answer 5

Structural Maintenance of Chromosomes

Question 6

PCNA

Answer 6

Proliferating cell nuclear antigen - replication factor DNA clamp

Question 7

MSH2-6

Answer 7

Mismatch repair protein

Question 8

Other functions of Cohesin

Answer 8

• Promotes attachment of spindle
• Compacts chromatids intra-chromatid
• Promotes repair of damage by recombination

Question 9

Cohesinopathies

Answer 9

• Syndromes causing birth defects from cohesion of subunits and/or cofactors failing

e.g. Roberts Syndrome - more Mi failure + apoptosis

Question 10

Other mean of sister chromatids cohesion - DNA catenation

Answer 10

Physical intertwining of sister chromatids
- Occurs during DNA replication and can be maintained until anaphase

Question 11

Importance of centromere

Answer 11

• Allows chromatids to separate
• Transcriptionally inert
• CENP-A replaces histone H3 in nucleosomes

Question 12

Kinetochore + its role

Answer 12

• Complex of proteins that assemble centromere
• Provides the link to spindle microtubules
• Provides directionally to chromosome movement

Question 13

What are centrosomes?

Answer 13

• Replicates in G1/S phase
• Initiates microtubule assembly

Question 14

When the chromatids are ready for anaphase

Question 15

Motor proteins

Answer 15

The microtubule is used like a molecular tightrope where motor proteins attach to kinetochore + microtubule and move in ‘steps’

Using their 2 ‘feet’ using to coordinate movement using energy from ATP hydrolysis