Chapter 8.4

Question 1

Cell Cycle

Answer 1

The series of events that take place in a cell leading to its division

Question 2

Interphase

Answer 2

Active preparation for cell division. In which most eukaryotic cells spend their time.

Question 3

What does interphase include

Answer 3

G1 PHASE : Normal cell function and cell
growth
S PHASE : DNA Replication

G2: PHASE: Additional growth and preparation for division

Question 4

After Interphase

Answer 4

The cell divides in Mitosis

Question 5

In what phase does replication occur

Answer 5

Interphase

Question 6

cytokinesis

Answer 6

The process in which a eukaryotic sperates into two identical daughter cells

Question 7

What happens to the newly formed daughter cells

Answer 7

The enter the cell cycle at interphase

Question 8

GAP 1 PHASE

Answer 8

Normal Cell function and growth

The cell grows, carries out basic functions and produces molecules needed to build new organelles and other components it will require if it divides

Question 9

A cell in G1 is sensitive to what

Answer 9

To external signals that tell it whether it should

1. Divide
2. Stop to repair damaged DNA
3. Die
4. Enter a non dividing stage G0

Question 10

G0 PHASE

Answer 10

a cell continues to function, but it does not replicate its DNA or divide
. At any given time most cells are in this stage
. It is reversible

Question 11

What cells are permanently in G0

Answer 11

Muscle Cells
Nerve Cells
which explains why the brain does not grow after it reaches its adult size and brain damage is often irreparable

Question 12

S (synthesis) phase what 2 things that occur

Answer 12

1.Dna Replication

enzymes replicate the cell’s genetic material and repair damaged DNA.

2. Duplication of Centrosomes

Question 13

Why did biologist mistakenly believed that interphase was an inactive time

Answer 13

Because the Chromatin is unwound and therefore barely visible.

Question 14

The product of S Phase ( DNA Replication) is

Answer 14

At the end of replication are 2 sister chromatids ( that are not visible under the microscope as yet)

Question 15

What are CENTROSOMES

Answer 15

Strucures that organize the proteins that will move the chromosomes during mitosis.

Question 16

What do centrosomes consist of

Answer 16

a cloud of proteins enclosing a pair of barrel shapes CENTRIOLES

Question 17

What occurs in Gap Phase 2

Answer 17

1. the cell continues to grow
2. prepares to divide
   . Produces the proteins that will coordinate the movement of the chromosomes during mitosis
   . Dna condenses more tightly ( signals that mitosis will begin and interphase is about to end)

Question 18

Explain the events of the cell cycle

Answer 18

Interphase is the period in which the cell prepares for division

1. G1 ( Zygote- first cell) Cells increase in size in Gap 1. The G1 checkpoint control mechanism ensures that everything is ready for DNA synthesis.
2. G0 A resting phase where the cell has left the cycle and has stopped dividing.
3. S DNA replication occurs during this phase.
4. G2 During the gap between DNA synthesis and mitosis, the cell will continue to grow. The G2 checkpoint control mechanism ensures that everything is ready to enter the M (mitosis) phase and divide.
5. M Cell growth stops at this stage and cellular energy is focused on the orderly division into two daughter cells. A checkpoint in the middle of mitosis (Metaphase Checkpoint) ensures that the cell is ready to complete cell division.

Question 19

Explain the two packaging stages of DNA and when they occur

Answer 19

CHROMATIN : DNA is loosely packed in the nucleus and available for DNA replication and protein synthesis. ( G1, beginning of S phase)

2 CHROMOSOME: Tightly wounded dna.
Begins shortly after replication. In (G2), it begins to condense in preparation for mitosis cell division.

Question 20

A Cellthat has completed interphase has how much DNA than a cell at the the beginning.

Answer 20

double: from dna replication in the S phase

Question 21

overall what happens in Mitosis to the cell

Answer 21

Separates the genetic material that was replicated in the s phase into 2 daunter cells.

Question 22

MITOTIC SPINDLE

Answer 22

An array of proteins that ensures that the chromosomes are distributed evenly in two sets that are then pulled to the opposite poles of the cell.

. It consists of microtubles that form the the fibers that grow outward front the centrosome

Question 23

The mitotic Spindle aligns Chromosomes how

Answer 23

The mitotic spindle consists of microtubles that form the fibers that grow outward from two centrosomes ( proteins and centrioles). The spindle fibers push and pull to align the chromosomes.

Question 24

the 6 Phases of Mitosis

Answer 24

Prophase
Prometaphase
Metaphase
Anaphase
Telophase
Cytokinesis

Question 25

PROPHASE

Answer 25

."pro" before . The first stage of cell division ( mitosis) 1.Dna coils up very tightly (chromosome),shortening and thickening the CHROMOSOMES(The sister chromatids recently replicated becomes visible) . They are arranged randomly in the nucleus 2. The CENTROSOMES move to the poles of the the cell, as they do this 3. MITOTIC SPINDLE begins to form 4. NUCLEOLUS disappears

Question 26

PROMETAPHASE

Answer 26

. "before metaphase" . Occurs immediately after the formation of the spindle. 1. Nuclear envelope (and associated endoplasmic reticulum) breaks up into small pieces , enabling the spindle fibers to reach the chromosomes. 1B. The chromosomes are loose within the cell 2. Meanwhile, proteins called kinetochores begin to assemble on each centromere; these proteins attach the chromosomes to the spindle fibre. 3. The spindle fibres attach to the kinetochores on chromosomes

Question 27

KINETOCHORES ( kineto- + chora, space)

Answer 27

Proteins that attach the chromosomes at their centromere to the spindle fiber. . They are formed during pro metaphase, they begin to assemble at each CENTROMERE

Question 28

Explain the relationship of MITOTIC SPINDLES, MICROTUBULES AND SPINDLE FIBRES

Answer 28

1. MICROTUBULES: are fibres that grow outward from 2 centrosomes 2. SPINDLE FIBRES: are the microtubules that attaches to the kinetochores of centromeres 3. MITOTIC SPINDLE: collectively refers to all the microtubules

Question 29

Metaphase

Answer 29

. meta ( means middle) | Chromosomes are aligned in the center/ middle / equator of the cell by the mitotic spindle attached kinetochores

Question 30

Why are Chromosomes are aligned in the center/ middle / equator of the cell by the mitotic spindle.

Answer 30

This alignment ensures that each cell will contain one sister chromatid from each duplicated chromosome.

Question 31

ANAPHASE

Answer 31

1. CENTROMERES split as MITOTIC SPINDLE PULLS sister CHROMATIDS apart. 2. Some Spindle fibres shorten reeling in sister chromatids to opposite poles of the cell near the centrosomes. 3. Others lengthen in a way that moves the poles further apart stretching the dividing cell.

Question 32

TELOPHASE (telos, end)

Answer 32

. The final stage of mitosis 1. Nuclear envelope and nucleolus forms at each pole. ( opposite of pro metaphase) The cell has two nuclei 2. Chromosomes decondenses ( opposite of prophase) 3.The mototic spindle disassembles The division of the genetic material is complete.

Question 33

CYTOKINESIS

Answer 33

organelles and macromolecules are distributed into two forming daughter cells, which then physically separate.

Question 34

CLEAVAGE FURROW

Answer 34

In an animal cell, is the first sign of cytokinesis. | a slight indentation around the middle of the cell

Question 35

What causes the cleavage furrow

Answer 35

A contractile ring of actin and myosin proteins that form beneath the cell membrane

Question 36

CELL PLATE

Answer 36

The first sign of cytokinesis in plants. | ( a dividing plant cell must construct a new wall that separates the two daughter cells

Question 37

How is the CELL PLATE form

Answer 37

vesicles from the Golgi apparatus travel along microtubules, delivering structural materials such as cellulose fibers, other polysaccharides and proteins to the midline of the dividing cell.

Question 38

Although cytokinesis follows mitosis give an example of an exception

Answer 38

Some types of green algae and slime mold, exist as enormous cells containing thousands of nuclei, the product of many rounds of mitosis without cytokinesis

Question 39

What are the three main events of the cell cycle?

Answer 39

The three main events are interphase, during which the cell grows and replicates its DNA, mitosis, during which the DNA divides, and cytokinesis, during which the cytoplasm divides.

Question 40

What happens during interphase

Answer 40

During interphase, a cell grows and produces proteins so that its normal biochemical functions proceed. DNA replicates during interphase as a cell prepares to divide

Question 41

How does the mitotic spindle form, and what is its function?

Answer 41

The mitotic spindle is composed of microtubules associated with cytoskeleton proteins. The spindle originates from centrosomes that are at opposite ends of the cell. Spindle fibers grow across to join at the midline of the cell. The function of the mitotic spindle is to form “trackways” for the movements of chromosomes as cells divide.

Question 42

What happens during each phase of mitosis

Answer 42

The events of mitosis include: • Prophase: chromosomes condense and become visible; mitotic spindle forms • Prometaphase: nuclear envelope breaks up; spindle fibers attach to kinetochores on each chromosome • Metaphase: chromosomes line up on equator of cell • Anaphase: sister chromatids separate and move to opposite poles of the cell • Telophase: nuclear membranes reassemble around the daughter nuclei; chromosomes decondense; spindle disappears

Question 43

5. Distinguish between mitosis and cytokinesis

Answer 43

Mitosis is the division of duplicated chromosomes into new daughter nuclei. Cytokinesis is the division of cytoplasm and organelles into two new daughter cells and the separation of these cells.