Question

name: ______________________________ annotation expectations: answer questions and write a sentence to justify your answer. exit ticket (10 mins) diagram: normal cells (with + growth factors → cells divide; - growth factors → no division) and cancer cells (± growth factors → cells divide) observe the diagram above. describe the control of the cell cycle as it relates to normal cells v. cancer cells. use the table below to provide the answer. table: checkpoint (g1, g2, metaphase) | normal cells | cancer cells

Explanation:

To solve this, we analyze the cell cycle checkpoints for normal and cancer cells:

G1 Checkpoint:

• Normal Cells: Proceed to S phase (DNA replication) only with positive growth factors; stop with negative growth factors (controlled division).
• Cancer Cells: Divide regardless of growth factor signals (uncontrolled, bypass G1 checkpoint).

G2 Checkpoint:

• Normal Cells: Check for DNA damage/errors; repair or arrest if issues (ensures genome integrity).
• Cancer Cells: Often bypass G2 checkpoint, dividing with damaged DNA (no proper error correction).

Metaphase (Spindle Checkpoint):

• Normal Cells: Wait for all chromosomes to attach to spindles; proceed to anaphase only when aligned (ensures equal division).
• Cancer Cells: May skip this checkpoint, leading to aneuploidy (abnormal chromosome number) in daughter cells.

Checkpoint	Normal Cells	Cancer Cells
G2	Check DNA integrity; repair/arrest if damaged.	Bypass checkpoint; divide with damaged DNA.
Metaphase	Wait for chromosome-spindle attachment; proceed when aligned.	Skip checkpoint; divide with misaligned chromosomes (aneuploidy risk).

Justification:

Normal cells follow cell cycle checkpoints (G1, G2, metaphase) to ensure controlled, error - free division (e.g., G1 needs +growth factors, G2 checks DNA, metaphase checks spindle attachment). Cancer cells bypass these checkpoints, leading to uncontrolled, abnormal division (e.g., divide with -growth factors, ignore DNA damage, or misaligned chromosomes).

Answer:

To solve this, we analyze the cell cycle checkpoints for normal and cancer cells:

G1 Checkpoint:

• Normal Cells: Proceed to S phase (DNA replication) only with positive growth factors; stop with negative growth factors (controlled division).
• Cancer Cells: Divide regardless of growth factor signals (uncontrolled, bypass G1 checkpoint).

G2 Checkpoint:

• Normal Cells: Check for DNA damage/errors; repair or arrest if issues (ensures genome integrity).
• Cancer Cells: Often bypass G2 checkpoint, dividing with damaged DNA (no proper error correction).

Metaphase (Spindle Checkpoint):

• Normal Cells: Wait for all chromosomes to attach to spindles; proceed to anaphase only when aligned (ensures equal division).
• Cancer Cells: May skip this checkpoint, leading to aneuploidy (abnormal chromosome number) in daughter cells.

Checkpoint	Normal Cells	Cancer Cells
G2	Check DNA integrity; repair/arrest if damaged.	Bypass checkpoint; divide with damaged DNA.
Metaphase	Wait for chromosome-spindle attachment; proceed when aligned.	Skip checkpoint; divide with misaligned chromosomes (aneuploidy risk).

Justification:

Normal cells follow cell cycle checkpoints (G1, G2, metaphase) to ensure controlled, error - free division (e.g., G1 needs +growth factors, G2 checks DNA, metaphase checks spindle attachment). Cancer cells bypass these checkpoints, leading to uncontrolled, abnormal division (e.g., divide with -growth factors, ignore DNA damage, or misaligned chromosomes).