T4 Module 1

Question 1

cell replication in prokaryotes vs eukaryotes

Answer 1

BINARY FISSION: prokaryotes
CELL CYCLE: eukaryotes

Question 2

binary fission process

Answer 2

1) DNA attached via pr- to inside of plasma membrane (ORIGIN OF APPLICATION)
2) DNA replication continues along plasma membrane
3) once DNA @ opposite end, cell splits along midpoint

Question 3

stem cell types

Answer 3

SATELLITE STEM CELLS: can replaces non-reproducing specialized cells (e.g. muscle regeneration)

QUIESCENT cells -> MYOBLAST -> MYOFIBRE
activated, proliferated, differentiated, fused

Question 4

cell cycle stages

Answer 4

INTERPAHSE
G1: cell growth
S: DNA synthesis
G2: cell growth

chromosomes duplicated and condensed

MITOSIS
Prophase (condense)
- centromeres condense
- centrosomes radiate microtubules + migrate to opposite poles
Prometaphase (attach)
- nuclear envelope breaks down
- kinetochore microtubules attach to centromeres on kinetochores (specialized pr- on either side of centromere)
Metaphase (middle)
- chromosomes align on metaphase plate
- microtubules facilitate
Anaphase (split)
- kinetochore microtubules shorten, pull sis chromatids apart via separase enzyme
- polar microtubules elongate the cell
Telophase (reset)
- nuclear envelope reforms
- chromosomes decondense
- microtubules depolymerized (broken down)

CYTOKINESIS
animals
- contractile ring (grows in middle of cell) -> cleavage furrow
plants
- new cell wall built on cell plate in middle of dividing cell

Question 5

number of inherited chromosomes

Answer 5

24 chromosomes total
23 homologous
1 sex chromosome

Question 6

when is cyclin-CDK used in the cell cycle?

Answer 6

G1->S: G1/S cyclin-CDK complex
- helps move G1-S
- preps for DNA replication (e.g. increased histone expression)

S: S cyclin-CDK complex
- helps initiate DNA synthesis

G2->Mitosis: M cyclin-CDK complex
- initiates mitosis
(e.g. via phosphorylation of pr- for nuclear membrane breakdown and microtubule activity)

Question 7

what is cyclin-CDK? When is used the most?

Answer 7

cyclin is a mitosis promoting factor
alongside cyclin dependant kinase (CDK), it controls the cell cycle

cyclin-CDK complex phosphorylated proteins involved in cell division

Question 8

cell cycle checkpoints

Answer 8

1) DNA damage checkpoint (G1)
- any damaged DNA?

2) DNA replication checkpoint (G2)
- all DNA replicated?

3) Spindle assembly checkpoint (M)
- all chromosomes attached to spindle?

Question 9

example of DNA damage checkpoint activation

Answer 9

• genes that inhibit cell cycle normally off
• when DNA damaged, pr- kinases activated + phosphorylate gene p53
• activated p53 acts as transcription factor, turns on CDK inhibitor genes
• G1/S cyclin-CDK complex blocked, G1 phase paused

Question 10

example of spindle assembly checkpoint activation

Answer 10

• unattached kinetochores send “wait” signal
• recruits spindle assembly checkpoint pr-
• when all microtubules attached, pr- removed and anaphase continues