4.1

Question 1

Cell division in prokaryotes (name and steps)

Answer 1

Binary fission
1. DNA anchored to inside of plasma membrane by proteins
2. DNA replication begins along origin of replication region
3. Newly synthesized DNA also anchored
4. Cell elongates ~2x its size
5. Constricts along midpoint
6. New cell membrane + wall synthesize to form two identical daughter cells

Question 2

Cell division in eukaryotes (name and phases)

Answer 2

Mitosis
Interphase:
- Gap 1 (G1)
- Synthesis (S)
- Gap 2 (G2)
M phase:
- Mitosis
- Cytokinesis
Quiescence:
- G0

Question 3

Stem cells (traits)

Answer 3

• can reproduce indefinitely
• differentiate into specialized cells
• in adults: can no longer differentiate into every type of cell in the organism, mostly used for repair/replacement
• non-dividing stem cells: quiescent SC

Question 4

Example of stem cells repairing adult skeletal muscle tissue

Answer 4

• quiescent SC activate
• proliferate (multiply)
• differentiate into myoblasts
• become myofibers and cannot divide anymore

Question 5

Mitosis steps

Answer 5

1. Prophase: chromatin fibers condense into chromosomes, centrosomes radiate microtubules forming a mitotic spindle, nuclear envelope deforms
2. Prometaphase: microtubules attach to centromeres of X at kinetochores
3. Metaphase: chromosomes alligned at center of cell (metaphase plate)
4. Anaphase: microtubules pull chromatids apart
5. Telophase: nuclear envelope reforms, chromatids decondense

Question 6

Interphase steps

Answer 6

G1: cell matures and behaves normally, will enter G0 if cannot replicate further
S: doubles DNA so each chromosome has 2 sister chromatids
G2: cell continues to grow, (in plants, chloroplasts divide in this phase)

Question 7

2 parts of the chromosome

Answer 7

centromere and chromatid(s)

Question 8

kinetochores

Answer 8

protein structures on the centromere of chromosome for microtubules to attach

Question 9

Cytokinesis

Answer 9

Animal cells:
- contractile ring forms and splits it into 2 daughter cells
Plant cells:
- lay down new cell wall along cell plate region (middle)

Question 10

Cyclin

Answer 10

protein which activates cyclin-dependent kinases to control progression of the cell cycle

Question 11

Kinases

Answer 11

enzymes that activate/deactivate other proteins

Question 12

cyclincyclin-dependent kinase (CDK) complexes

Answer 12

G1/S cyclin-CDK complex: prepares cell for replication
S cyclin-CDK complex: initiate DNA synthesis
M cyclin-CDK complex: prep for mitosis

Question 13

cell cycle checkpoints

Answer 13

cyclin-CDK activity is blocked if errors are found
before S phase: DNA damage
before M phase: DNA all replicated
before anaphase: all chromosomes attached to spindle

Question 14

DNA damage occurs

Answer 14

• activates kinases that phosphorylate p53, allowing it to accumulate
• p53 turns on genes that inhibit the cell cycle