Module 2 Mitosis

Question 1

3 cycles in the cell cycle

Answer 1

• Chromosome cycle
• Cytoplasmic cycle
• Centrosome cycle

Question 2

What cycle in the cell cycle?

DNA synthesis alternates with mitosis. During DNA synthesis, each double-helical DNA molecule is replicated into two identical daughter DNA molecules and during mitosis the duplicated copies of the genome are ultimately separated.

Answer 2

Chromosome cycle

Question 3

What cycle in the cell cycle?

Cell growth alternates with cytokinesis (____________). During cell growth many other components of the cell become double in quantity and during cytokinesis, a cell, as a whole, divides into two. Usually, karyokinesis is followed by cytokinesis but sometimes cytokinesis does not follow and results into the multinucleate cell, e.g., cleavage of egg in Drosophila

Answer 3

Cytoplasmic cycle
cytokinesis (cytoplasmic division)

Question 4

What cycle in the cell cycle?

Both chromosome cycle and cytoplasmic cycle require that the _______ be inherited reliably and duplicated precisely in order to form the two poles of the mitotic spindle; thus, this cycle forms the third component of cell cycle

Answer 4

Centrosome cycle
centrosome

Question 5

Structure and Organization of Chromosome and their lengths (8)

Answer 5

1. DNA double helix: 2 nm
2. Nucleosome (Core proteins + DNA): 11 nm
3. Chromatosome (Nucleosome + H1): 11 nm
4. Solenoid chromatin fiber ( 6 Nucleosomes + linker): 30 nm
5. Scaffold loop (Radial loop on Scaffold protein): 300 nm
6. The 300-nm fibers -> 250 nm
7. Tight coiling to produce chromatid of a chromosome: 700 nm
8. Chromosome: 1400 nm

Question 6

Each nucleosome consists of _____ histone proteins around which the DNA wraps _____ times

Answer 6

eight
1.65 times

Question 7

consists of a nucleosome plus the H1 histone

Answer 7

chromatosome

Question 8

there are ____ nucleosomes in solenoid chromatin fiber

Answer 8

6

Question 9

What phase?

• the nuclear envelope stars to dissociate into ______
• the membranous organelles (Golgi and ER) fragment and disperse toward the periphery of the cell
• the nucleolus disappears
• centrosomes begin to move to opposite poles
• microtubules extend between the centrosomes, pushing them farther apart as the microtubule fibers lengthen
• sister chromatids begin to coil more tightly with the aid of ________ and become visible under a light microscope

Answer 9

Prophase

• small vesicles
• condensin proteins

Question 10

“first change phase”

Answer 10

prometaphase

Question 11

What phase?

• many processes that were begun in prophase continue to advance
• the remnants of the nuclear envelope fragment
• the mitotic spindle continues to develop
• chromosomes become more condensed and discrete
• each sister chromatid develops a protein structure called ________ in the centromeric region
• mitotic fiber attaches to a chromosome , the chromosome will be oriented until the kinetochores of sister chromatids face the opposite poles.
• polar microtubules overlap each other midway between the two poles and contribute to cell elongation.

Answer 11

Prometaphase

• kinetochore

Question 12

proteins of the _______ attract and bind mitotic spindle microtubules

Answer 12

kinetochore

Question 13

Spindle microtubules that do not engage the chromosomes are called _________. These microtubules overlap each other midway between the two poles and contribute to cell elongation.

Answer 13

polar microtubules

Question 14

_________ are located near the poles, aid in spindle orientation, and are required for the regulation of mitosis.

Answer 14

Astral microtubules

Question 15

the “change phase”

Answer 15

Metaphase

Question 16

What phase?

• all the chromosomes are aligned in a plane called the ____________, midway between the two poles of the cell
• the sister chromatids are still tightly attached to each other by _____ proteins
• the chromosomes are maximally condensed

Answer 16

Metaphase

• metaphase plate or the equatorial plane
• cohesin

Question 17

the “upward phase”

Answer 17

Anaphase

Question 18

What phase?

• the cohesin proteins degrade, and the sister chromatids separate at the centromere
• Each chromatid, now called a chromosome, is pulled rapidly toward the centrosome to which its microtubule is attached.
• The cell becomes visibly elongated (oval shaped) as the polar microtubules slide against each other at the metaphase plate where they overlap.

Answer 18

Anaphase

Question 19

the “distance phase”

Answer 19

Telophase

Question 20

What phase?

• the chromosomes reach the opposite poles and begin to decondense (unravel), relaxing into a chromatin configuration
• mitotic spindles are depolymerized into tubulin monomers used to assemble cytoskeletal components
• nuclear envelopes form around the chromosomes, and nucleosomes appear within the nuclear area

Answer 20

Telophase

Question 21

mitotic spindles are depolymerized into _______ used to assemble cytoskeletal components

Answer 21

tubulin monomers

Question 22

“cell motion”

Answer 22

cytokinesis

Question 23

is the second main stage of the mitotic phase during which cell division is completed via the physical separation of the cytoplasmic components into two daughter cells

Answer 23

cytokinesis

Question 24

In cells such as animal cells that lack cell walls, cytokinesis follows the onset of anaphase.

• A contractile ring composed of ________ forms just inside the plasma membrane at the former metaphase plate. This pull the equator of the cell inward, forming a fissure. This fissure, or “crack,” is called the _________.

Answer 24

actin filaments
cleavage furrow

The furrow deepens as the actin ring contracts, and eventually the membrane is cleaved in two.

Question 25

In plant cells, a new cell wall must form between the daughter cells.

• During interphase, the _________ accumulates enzymes, structural proteins, and glucose molecules prior to breaking into vesicles and dispersing throughout the dividing cell.
• During telophase, these Golgi vesicles are transported on microtubules to form a _________ (a vesicular structure) at the metaphase plate.
• There, the vesicles fuse and coalesce from the center toward the cell walls; this structure is called a _______.
• As more vesicles fuse, the cell plate enlarges until it merges with the cell walls at the periphery of the cell.
• Enzymes use the _______ that has accumulated between the membrane layers to build a new cell wall.
• The Golgi membranes become parts of the plasma membrane on either side of the new cell wall.

Answer 25

Golgi apparatus
phragmoplast
cell plate
glucose

Question 26

Chromosome types (4)

Answer 26

• metacentric
• acrocentric
• telocentric
• sub-metacentric

Question 27

Cell size is limited.

• Volume increases faster than surface area.
• _______ must allow for adequate exchange of materials
• Cell growth is coordinated with _____
• Cells that must be large have ______ shapes.

Answer 27

Surface area
division
unique

Question 28

How many chromosomes are in the daughter cells of mitosis and meiosis?

Answer 28

46 - mitosis
23 - meiosis