Lecture #10- The Cell Cycle

Question 1

what are the 2 key roles of cell division

Answer 1

reproduction:
- meiosis facilitates sexual reproduction
- unicellular organism divide to produce genetically identical offspring
development:
- multicellular organisms are compose fo many cells which arise from mitosis

Question 2

What is prokaryotic cell division and draw it out

Answer 2

• are unicellular organisms that have a single circular chromosome and no nucleus therefore their cell divisions cycle is much simpler than eukaryotes
• divide by binary fission (NOT MITOSIS)

Question 3

describe the prokaryotic growth curve and draw it out

Answer 3

• growth is exponential
  1. lag phase - cell are still growing and not dividing
  2. log (exponential phase) - cells are dividing
  3. stationary phase - division = death - due to the accumulation of waste, depletion of nutrients
  4. death phase - division &laquo_space;death

Question 4

define:
- chromosome
- chromatid
- centromere
- kinetochore

Answer 4

• one copy of genetic info
• product of DNA replication, sister chromatids stay associated at the centromere
• site of attachment of sister chromatids and microtubules at kinetochore
• protein complex that assembles at centromere

Question 5

Describe the 4 cell cycle phases and draw it out

Answer 5

G1 - normal cell activity, cell is deciding to divide
S - synthesis DNA, DNA replication
G2 - normal cell activities, cellis preparing to divide, 2x DNA
M - mitosis, separation of chromatids

Question 6

what are the 6 phases of mitosis

Answer 6

1. prophase
2. prometaphase
3. metaphase
4. anaphase
5. telophase
6. cytokinesis

Question 7

What is prophase and draw it out

Answer 7

• chromosomal condensation to facilitate chromosomal movements later in mitosis
• necessary to package the DNA into moveable structures
• condensation is accomplished by histones

Question 8

what is prometaphase and draw it out

Answer 8

• the fishing phase
• nuclear envelope breakdown
• MT search and capture the DNA
• centrosomes can access the DNA to bind to the centromere, the centrosomes are in cytosol and cannot access the DNA until the nuclear envelope breaks down

Question 9

what is the metaphase and draw it out

Answer 9

• involves the movement of the sister chromatids to the metaphase plate, these movements require MT motor action and are accomplished by kinetochore MT
• chromosomes are moved by: polarization and depol of MT
  3 MTS:
• kinetochore: attach and move chromosome
• polar/overlapping MT: elongate the cell
• astral MT: anchor the MTOC (centrosomes) at membrane

Question 10

what is anaphase and draw it out

Answer 10

• separation of chromatids (each chromatid is now called a chromosome)
• kinetochore MT - shorten by depolarization or dyenin
• polar/overlap MT - push against each other to elongate the cell due to the bipolar kinesin walking to the positive ends

Question 11

what is telophase and draw it out

Answer 11

• nuclear envelope reformation and chromosomal decondensation
• in order for the completion of mitosis, the daughter cells must reform their nuclear envelop and separate their cytoplasm

Question 12

what is cytokinesis and draw it out

Answer 12

• splitting of cytoplasm
• microfilaments bundle at metaphase plate
• myosin pulls the MF to construct the rings of MF

Question 13

Cell Cycle control: 3 checkpoints and draw it out

Answer 13

• decision points to decide when a cell should divide
  1. Restriction point (G1): are there signals to divide, is there enough space?, are there enough nutrients?
  2. G2 Checkpoint (M phase checkpoint): is DNa replication complete (are there any primers left on the DNA)
  3. Metaphase checkpoint: are all kinetochores attached by MT?