Segregating duplicate chromosomes flipped classroom

Question 1

How can you measure and compare cell complexity to other structures?

Answer 1

• distinct components require distinct building blocks
• directions specified by the coding density per DNA segment
• PTM add another level of complexity influenced by cell-environmental interactions

Question 2

Why do cells have periods of biosynthesis and growth before starting mitosis?

Answer 2

• DNA must be duplicated before cell division to make sure there is an available copy of each chromosome for each daughter cell
• to make sure that resulting daughter cells have enough of the required materials (enzymes, membranes, organelles) to survive

Question 3

What are the important sections of interphase period of cell cycle?

Answer 3

Before DNA duplication

1. G1 gap phase
2. G0
   - ——————-
3. S phase (synthesis)
4. G2 gap phase
5. M phase (mitosis nuclear division and cytokinesis cytoplasmic division)

Question 4

G1

Answer 4

cell growth (protein and membrane synthesis) before DNA duplication

Question 5

G0

Answer 5

cell differentiation before DNA duplication

Question 6

S phase

Answer 6

• DNA synthesis (duplication)
• centrosome duplication
• histone synthesis

Question 7

G2

Answer 7

further growth after DNA duplication to allow cells to make and check all the components necessary for cell division

Question 8

Centrosome duplication mechanism

Answer 8

G1 phase: one centrosome becomes one separated centrosome
S phase: two immature centrosomes
M phase: two mature centrosomes

Question 9

What is the essential problem of mitosis?

Answer 9

The essential problem of mitosis is attaching kinetochores on sister chromatids to opposite ends of the spindle

Question 10

How is the stable attachment of kinetochores on sister chromatids achieved?

Answer 10

When MT from the opposite pole binds to second kinetochore, sister kinetochores are thought to sense tension across MT-binding sites, triggering an increase in MT binding affinity and locking the correct attachment in place.

Question 11

Why is the incorrect attachment of kinetochores on sister chromatids unstable?

Answer 11

1 of the 2 microtubules tend to dissociate

Question 12

How can tension be used as a check point mechanism for attaching kinetochores on sister chromatids to opposite ends of the spindle?

Answer 12

Kinetochores sense correct attachment through tension
When a sister-chromatid pair is properly bi-oriented on the spindle, the 2 kinetochores are pulled in opposite directions by strong poleward forces. Sister-chromatid cohesion resists these poleward forces, creating high levels of tension within the kinetochores.

Question 13

What strategies do cells use in order to deal with the problem of segragating millimeters of DNA into 2 daughter cells?

Answer 13

1. To prevent large sizes of DNA, package DNA into pieces
2. Condense chromatin to chromosomes
3. Replicate all DNA before initiating segragation
4. Couple sister chromatids with cohesin as they are made by DNA replication, so sister chromatids are in a defined position relative to one another
5. Develop special machine (mitotic spindle) for segragation