ONS PRACTICE EXAM QUESTIONS AND
DETAILED SOLUTIONS 2026
▶ Synthesis Phase (S phase). Answer: -DNA replicates
-Results in the formation of identical pairs of DNA (chromatids)
-which are attached a t the centromere
-lasts 2-10 hours
▶ Mitotic Phase (M phase). Answer: -Replicated chromosomes are
aligned, separated, and move into 2 new, identical daughter cells
-takes about 30-60 minutes
▶ Major points of cell regulation are entry and exit from. Answer: -G1
checkpoint
-S Phase
-G2 checkpoint
,-M phase
▶ Restriction Point. Answer: -The transition from the resting phase into an
actively dividing phase (G0-G1) is a point where cellular transformation can
occur
-During this time, cells pass through a transition phase known as a
restriction point
-Extracellular growth factors trigger reentry into G1, and GF are required to
send the cells past the restriction point, or the point of no return
▶ G0 Phase (resting phase). Answer: -After mitosis, cells may enter back
into the G1 phase or go into a resting phase, known as G0
-Most cells in the human body reside in G0
▶ -Exceptions to this are those that are (Resting in G0 phase). Answer: -
Exceptions to this are those that are metabollically active, such as
-granulocytes
-and the epithelium of the GI tract
▶ Cell Cycling Time. Answer: Amount of time from mitosis to mitosis
,▶ Cell cycle video and image. Answer:
http://highered.mheducation.com/sites/0072495855/student_view0/chapter
2/animation__how_the_cell_cycle_works.html
▶ Check points in the Cell Cycle: Keeping it All Under Control. Answer: -
The cell cycle is carefully controlled through a series of checkpoints
-Variation in duplication or distribution of chromosomes during cell division
can alter the genetic information passed on to daughter cells, leading to
cellular dysfunction and disease, such as cancer
-These checkpoints monitor for DNA integrity and control progression
through mitosis
▶ Progression through the cell cycle is controlled through two proteins:.
Answer: 1. cyclines (D, E, A, B)
2. Cyclin-dependent kinases (CDKs)
-Cyclin-CDK complex allows the cell to progress through each phase of the
cell cycle
▶ Locations of proteins Cyclins (D, E, A, B) and CDKs. Answer: -(G0-G1) :
Cyclin D and CDK 4/6
, -Early S: Cyclin E and CDK 1/2
-Late S: Cyclin A and CDK 1/2
-G2: CDK 1/2 and cyclin A
-Before M: CDK 1 and Cyclin B
▶ Inhibitory proteins. Answer: -prevent progression of the cycle when DNA
damage is detected
-An example of an inhibitory protein is p53 (AKA TP53)
▶ DNA Damage Checkpoints. Answer: -If DNA damage is present, cells
are programmed to stop dividing or undergo apoptosis (programmed cell
death)
-The retinoblastoma protein (Rb), p53, and p21 are some of the most well-
understood inhibitory proteins (IP)
▶ Inhibitory proteins p53. Answer: -Levels of this IP regulate several
important target genes
-Will increase when DNA damage is present
DETAILED SOLUTIONS 2026
▶ Synthesis Phase (S phase). Answer: -DNA replicates
-Results in the formation of identical pairs of DNA (chromatids)
-which are attached a t the centromere
-lasts 2-10 hours
▶ Mitotic Phase (M phase). Answer: -Replicated chromosomes are
aligned, separated, and move into 2 new, identical daughter cells
-takes about 30-60 minutes
▶ Major points of cell regulation are entry and exit from. Answer: -G1
checkpoint
-S Phase
-G2 checkpoint
,-M phase
▶ Restriction Point. Answer: -The transition from the resting phase into an
actively dividing phase (G0-G1) is a point where cellular transformation can
occur
-During this time, cells pass through a transition phase known as a
restriction point
-Extracellular growth factors trigger reentry into G1, and GF are required to
send the cells past the restriction point, or the point of no return
▶ G0 Phase (resting phase). Answer: -After mitosis, cells may enter back
into the G1 phase or go into a resting phase, known as G0
-Most cells in the human body reside in G0
▶ -Exceptions to this are those that are (Resting in G0 phase). Answer: -
Exceptions to this are those that are metabollically active, such as
-granulocytes
-and the epithelium of the GI tract
▶ Cell Cycling Time. Answer: Amount of time from mitosis to mitosis
,▶ Cell cycle video and image. Answer:
http://highered.mheducation.com/sites/0072495855/student_view0/chapter
2/animation__how_the_cell_cycle_works.html
▶ Check points in the Cell Cycle: Keeping it All Under Control. Answer: -
The cell cycle is carefully controlled through a series of checkpoints
-Variation in duplication or distribution of chromosomes during cell division
can alter the genetic information passed on to daughter cells, leading to
cellular dysfunction and disease, such as cancer
-These checkpoints monitor for DNA integrity and control progression
through mitosis
▶ Progression through the cell cycle is controlled through two proteins:.
Answer: 1. cyclines (D, E, A, B)
2. Cyclin-dependent kinases (CDKs)
-Cyclin-CDK complex allows the cell to progress through each phase of the
cell cycle
▶ Locations of proteins Cyclins (D, E, A, B) and CDKs. Answer: -(G0-G1) :
Cyclin D and CDK 4/6
, -Early S: Cyclin E and CDK 1/2
-Late S: Cyclin A and CDK 1/2
-G2: CDK 1/2 and cyclin A
-Before M: CDK 1 and Cyclin B
▶ Inhibitory proteins. Answer: -prevent progression of the cycle when DNA
damage is detected
-An example of an inhibitory protein is p53 (AKA TP53)
▶ DNA Damage Checkpoints. Answer: -If DNA damage is present, cells
are programmed to stop dividing or undergo apoptosis (programmed cell
death)
-The retinoblastoma protein (Rb), p53, and p21 are some of the most well-
understood inhibitory proteins (IP)
▶ Inhibitory proteins p53. Answer: -Levels of this IP regulate several
important target genes
-Will increase when DNA damage is present
