Lesson 19: Cell Cycle and Mitosis

Question 1

What is cytokinesis?

Answer 1

The cytoplasm of the cell containing two nuclei divides forming two daughter cells

Question 2

What is Prophase?

Answer 2

The beginning of mitosis:

• -Chromosomes condense
• -Mitotic spindles and centrosomes form in cytoplasm

Question 3

What happens during Metaphase?

Answer 3

Chromosomes line up single-file at the center of the cell

Question 4

What happens during Anaphase?

Answer 4

Chromosomes divide by being pulled apart by the mitotic spindles attached to the centrosomes

Question 5

What happens during Telophase?

Answer 5

Cytokinesis occurs and nuclear envelopes form around each group of chromosomes

Question 6

What is a kinetochore?

Answer 6

A region near the centromere of each chromosome that contains motor proteins that remove tubulin from the spindle fibers while it keeps the spindle attached to the chromosome

Question 7

What are the phases of the cell cycle?

Answer 7

• G1 Phase: 1st gap between the birth of the new cell and DNA replication. Cell grows, organelles are duplicated, and machinery are created to replicate DNA
• S Phase: DNA synthesis. Each single DNA molecule (chromosome) is copied to make two sister chromatids (also called chromosomes)
• G2 Phase: Cell growth, organelle duplication, preparation for cell division
• M Phase: Mitosis

Question 8

What is Interphase?

Answer 8

The interval made up by both gap phases (G1 and G2) and S phase during which cells do not divide.
Cells spend most of their time in Interphase

Question 9

How many DNA molecules are present at the end of S phase?

Answer 9

Twice as many as there are chromosomes

Question 10

What is a cell-cycle checkpoint?

Answer 10

A point at which the cells checks to see if all the steps of the preceding phase have been completed before moving to the next phase

Question 11

What is checked at the first cell-cycle checkpoint?

Answer 11

• Cell size
• Sufficient nutrient availability
• Growth factors (signals) from other cells are present

Question 12

What protein is increased when a cell receives a growth factor signal?

Answer 12

Cyclin, a protein which binds to enzyme Cyclin Dependent Kinase (CDK) , causing target proteins to be activated. This cascade causes the S-phase to begin

Question 13

Is there a checkpoint for passage from S-phase to G2-phase?

Answer 13

NO

Question 14

What is checked at the second checkpoint?

Answer 14

• Cell size

- Chromosome replication success

Question 15

What protein complex causes Mitosis to begin?

Answer 15

G2 Cyclin binds to CDK forming a complex called Mitosis Promoting Factor (MPF)

Question 16

What is checked at the final checkpoint?

Answer 16

During Metaphase of Mitosis all chromosomes are checked to see if they are attached to mitotic spindle fibers

Question 17

What causes a cell to pass from Mitosis back to the G1 phase?

Answer 17

The degradation of mitotic cyclin

Question 18

What happens during Prometaphase?

Answer 18

• -The nucleolus disappears and the nuclear envelope breaks down
• -Spindle fibers attach to the chromatids at the kinetochore

Question 19

How can muscle cells have multiple nuclei per cell?

Answer 19

Repeated Mitosis without Cytokinesis

Question 20

How might motor proteins assist in the process of pulling chromosomes toward the poles of the cell?

Answer 20

They change shape through phosphorylation or binding to ATP

–Motor proteins like kinesin and dynein change shape as they are phosphorylated or bind to ATP to produce movement

Question 21

How is plant cell cytokinesis different from animal cell cytokinesis?

Answer 21

A cell plate is formed in the middle of the dividing cell in plants, where as in animal cells a cleavage furrow is formed