BIO-Exam 4: Cell Cycle

Question 1

G1 phase

Answer 1

mitosis in interphase; the cell grows and prepares for DNA replication.

Question 2

G0 phase

Answer 2

A resting-state outside the active cell cycle; the cell is not dividing.

Question 3

Cyclin

Answer 3

Regulates the cell cycle at various checkpoints by activating CDKs

Question 4

Stem cell

Answer 4

No specific phase; undifferentiated cells capable of dividing and becoming specialized.

Question 5

S phase

Answer 5

Part of interphase; DNA replication occurs

Question 6

Quiescence

Answer 6

Synonymous with G0 phase; a reversible non-dividing state. Unlike G0

Question 7

Cyclin-dependent kinase (CDK)

Answer 7

Active at various checkpoints; enzymes that, when bound to cyclins, drive cell cycle progression.

Question 8

Totipotent

Answer 8

No cycle phase; stem cells that can become any cell type, including extra-embryonic tissues.

Question 9

G2 phase

Answer 9

Follows S phase in interphase; the cell prepares for mitosis by checking DNA and synthesizing proteins.

Question 10

Restriction point

Answer 10

Occurs late in G1 phase; the critical checkpoint where the cell commits to the cell cycle.

Question 11

Necrosis

Answer 11

Not part of the cycle; uncontrolled cell death due to damage or injury

Question 12

Pluripoten

Answer 12

Not cycle-specific; stem cells that can become any cell type except extra-embryonic tissues.

Question 13

M phase

Answer 13

The mitosis phase; the cell divides its nucleus and cytoplasm to form two daughter cells

Question 14

Growth factors

Answer 14

External signals that influence the G1 phase; they promote cell cycle entry and progression.

Question 15

Apoptosis

Answer 15

Not part of the cycle; programmed cell death used to eliminate damaged or unnecessary cells.

Question 16

Multipotent

Answer 16

Not cycle-specific; stem cells that can develop into multiple, but limited, cell types.

Question 17

Prophase

Answer 17

Early stage of M phase (mitosis); chromosomes condense and spindle begins to form.

Question 18

Centromere

Answer 18

on chromosomes during all mitotic phase(s); Sister chromatids are joined and kinetochores form.

Question 19

Aster microtubule

Answer 19

Forms in prophase/metaphase; helps anchor spindle poles to the cell cortex.

Question 20

Separase

Answer 20

Activated in anaphase; cleaves cohesin proteins to allow sister chromatid separation.

Question 21

Prometaphase

Answer 21

Between prophase and metaphase; nuclear envelope breaks down and spindle fibers attach to kinetochores.

Question 22

Mitotic spindle

Answer 22

Forms from prophase to metaphase; a structure of microtubules that separates chromosomes.

Question 23

Cohesin

Answer 23

Present from S phase until anaphase; protein complex that holds sister chromatids together.

Question 24

Cytokinesis

Answer 24

Follows telophase at the end of M phase; cytoplasm divides to form two daughter cells.

Question 25

Metaphase

Answer 25

Middle of M phase; chromosomes align at the cell’s equatorial plate.

Question 26

Kinetochore

Answer 26

Forms at centromeres in prometaphase; attaches chromosomes to spindle microtubules.

Question 27

Anaphase checkpoint

Answer 27

Occurs at metaphase-anaphase transition; ensures all chromosomes are properly attached before separation.

Question 28

Contractile ring

Answer 28

Forms during cytokinesis; actin-myosin structure that pinches the cell into two.

Question 29

Anaphase

Answer 29

Mid-to-late M phase; sister chromatids separate and move to opposite poles.

Question 30

Interpolar microtubule

Answer 30

Present in metaphase and anaphase; stabilize the spindle and push poles apart.

Question 31

Anaphase promoting complex (APC)

Answer 31

Activated at the metaphase-anaphase transition, triggers the degradation of securin and cyclin to start anaphase.

Question 32

Telophase

Answer 32

Late M phase; chromosomes decondense and nuclear envelopes reform

Question 33

Kinetochore microtubule

Answer 33

Active from prometaphase through anaphase; attaches to chromosomes and pulls them apart

Question 34

Securin

Answer 34

Present until anaphase; inhibits separase until Anaphase Promiting Complex (APC) degrades it, allowing chromatid separation.

Question 35

OUTLINE: Prophase

Answer 35

In prophase, the mitotic spindle begins to form as the two centrosomes—doubled during S phase—move to opposite poles, creating overlapping sets of microtubules. Meanwhile, chromosomes condense as nucleosomes coil into higher-order structures, preparing for division.

Question 36

OUTLINE: Prometaphase

Answer 36

The nuclear envelope breaks down as lamins are phosphorylated by Cyclin/CDK, disrupting the nucleus. Chromosomes attach to the spindle via kinetochores, which connect to microtubules, while other microtubule types (interpolar and aster) stabilize the spindle structure.

Question 37

OUTLINE: Metaphase

Answer 37

Chromosomes are tugged by microtubules from both poles and align at the center of the cell. Cohesin holds sister chromatids together, preventing separation at this point.

Question 38

OUTLINE: Anaphase

Answer 38

Once the spindle checkpoint is passed, APC is activated and degrades securin, freeing separase to break down cohesin and separate the sister chromatids. Kinetochore microtubules shorten as chromatids move apart, while interpolar microtubules push the spindle poles farther away.

Question 39

OUTLINE: Telophase

Answer 39

Separated chromosomes move to opposite poles as lamins are dephosphorylated and the nuclear envelope reforms around each set. This marks the re-establishment of two distinct nuclei.

Question 40

OUTLINE: Cytokinesis

Answer 40

The spindle determines where the cell will divide, and a contractile ring of actin forms at that site. The ring tightens progressively until the cell is physically split into two daughter cells.