Topic 9 Mitosis

Question 1

Cellular Division

Answer 1

• The ability of organisms to produce more of their own kind
• The continuity of life is based on the reproduction of cells, or cell division
• Mitosis and Meiosis

Question 2

Functions of Cellular Division
* In unicellular organisms:

Answer 2

• Division of one cell reproduces the
  entire organism

Question 3

• Multicellular eukaryotes depend on cell division for:

Answer 3

• Development from a fertilized egg
• Growth
• Repair

Question 4

Cell cycle:

Answer 4

the life of a cell from formation to
its own division

Question 5

daughter cells

Answer 5

Most cell division results in two daughter cells with identical genetic information
* The exception is meiosis:

Question 6

Genome

Answer 6

all the DNA in a cell
* A genome can consist of:
* A single DNA molecule (common in prokaryotic cells)
* A number of DNA molecules (common in eukaryotic cells)

Question 7

Chromatin

Answer 7

a complex of DNA and protein (histones) that condenses during cell division

Question 8

Sister chromatids:

Answer 8

joined copies of the original chromosome, attached along their lengths by cohesins

Question 9

Cohesins

Answer 9

protein complexes that attach sister chromatids

Question 10

• The centromere:

Answer 10

• The narrow “waist” of the duplicated
  chromosome
• Where the two chromatids are most closely attached
• Once separate, the chromatids are called chromosomes

Question 11

Interphase (G1, S, and G2)

Answer 11

• Cell growth and copying of chromosomes
  in preparation for cell division

Question 12

Mitotic phase (Mitosis and Cytokinesis)

Answer 12

• Mitosis: the division of the genetic material in the nucleus
• Cytokinesis: the division of the cytoplasm

Question 13

G1 phase:

Answer 13

First gap, cells increase in size, gets ready for S phase

Question 14

S phase:

Answer 14

Synthesis, DNA replication occurs

Question 15

G2 phase

Answer 15

Second gap, cells continue to grow,
gets ready for Mitosis

Question 16

G2 of Interphase (after s phase) 3

Answer 16

• A nuclear envelope enclose the nucleus
• Two centrosomes have formed
• Regions that organize microtubules
• Chromosomes duplicated in S phase cannot be seen, because they have not condensed

Question 17

Prophase 4

Answer 17

• chromatin fibers are tightly coiled into discrete chromosomes, becoming visable
• duplicated chromosomes appear as two sister chromatids joined at centromeres
• mitotic spindle begins to form
• centrosomes move away from each other

Question 18

prometaphase 5

Answer 18

• nuclear envelope fragments, chromosomes even more condense
• microtubules from each centresome invade nuclear area
• kinetochore on the centromere on each sister chromotid
• some microtubule become kinetochore microtubules, jerking chromosomes back and forth
• any non kinetochore microtubules elongate the cell

Question 19

Metaphase 3

Answer 19

• Centrosomes now at opposite poles of the cell
• Chromosomes have arrived at the metaphase plate
• An imaginary plane at the middle of the cell * Centromeres lie at metaphase plate
• Kinetochore of each sister chromatid attach to kinetochore microtubules

Question 20

Anaphase 4

Answer 20

• shorest phase of mitosis
• cohesios between chromotids are cleaved, allowing each pair to separate
• two new daughter chromosomes moving towards opposite poles
• centromeres lead, because microtubules attached to kinetochore

Question 20

Telophase 4

Answer 20

• two daughter nuclei formm
• nuclear envelope reappears
• chromosomes start to decondense
• mitosis is complete

Question 21

cytokinesis

Answer 21

• division of cytoplasm
• involves fomration of a cleavage furrow in animal cells

Question 22

The Mitotic Spindle:

Answer 22

• A structure made of microtubules that controls chromosome movement during mitosis

Question 23

centrosome

Answer 23

In animal cells, assembly of spindle microtubules begins in the centrosome
* Microtubule-organizing center (MTOC)

• the centrosome replicates during interphase
• two centrosomes migrate to oppoiste ends of the cell during prophase and prometaphase

Question 24

Kinetochores

Answer 24

are protein complexes associated with centromeres

Question 25

In anaphase, the cohesins are cleaved by

Answer 25

an enzyme called separase

Question 25

The microtubules shorten by

Answer 25

depolymerizing at their kinetochore ends

Question 26

Non-kinetochore microtubules

Answer 26

from opposite poles overlap and push against each other, elongating the cell

Question 26

Non-kinetochore microtubules

Answer 26

from opposite poles overlap and push against each other, elongating the cell

Question 27

In animal cells, cytokinesis occurs by.... In plant cells

Answer 27

a process known as cleavage, forming a cleavage furrow * Contractile ring of microfilaments a cell plate forms during cytokinesis * Vesicles contain cell wall material * Vesicles are derived f rom Golgi apparatus

Question 27

cell cycle control system

Answer 27

The cell cycle is directed by a distinct cell cycle control system, which is similar to a clock * The clock has specific checkpoints where the cell cycle stops until a go-ahead signal is received

Question 28

Cellular Checkpoints

Answer 28

* Changes in regulatory protein concentrations drives the cell cycle * Three important checkpoints are those in the G1, G2, and M phases * If the cell does not receive the go- ahead signal, it will exit the cycle, * Switches to an on-dividing state called the G0 phase v