W3 Mitosis

Question 1

G1 phase:

Answer 1

-Cell increases size and synthesises protein and rna

Question 2

G1 Checkpoint (G1/S transition)

Answer 2

-Cell decides whether to continue division or not
-DNA damage is main factor that determines this decision but other factors include: cell size, nutrient availability, growth factors, adequate energy store

Question 3

S phase:

Answer 3

-DNA and chromosome replication

Question 4

G2 Phase:

Answer 4

-Cell prepares for cell division
-Checking new chromatids for errors
-Transient arrest can occur in G2
-Shorter than G1 and more uniform in duration

Question 5

Late G2 Phase:

Answer 5

-Chromosomes start to condense
-Nucleolus and nuclear envelope visible

Question 6

G2 Checkpoint (G2/M Transition)

Answer 6

-Cells checks the DNA integrity and success of DNA replication during S phase
-Repairs occur if damage is present. If damage is irreversible, cell may undergo apoptosis

Question 7

Prophase:

Answer 7

**Early Prophase: **
-Centrioles move apart
-Chromosomes shorten and thicken and start to become visible
-Nucleolus beings to disappear

Middle Prophase:
-Centrioles continue to move apart
-Mitotic spindle begins forming
-Replicated chromosomes become visible

Question 8

Prometaphase (Late Prophase):

Answer 8

-Centrioles reach opposite sides of nucleus.
-Spindle begins to form
-Nuclear envelope begins to disappear

Question 9

Metaphase:

Answer 9

-Nuclear envelope has disappeared
-Replicated chromosomes, held together at centromere, align on equator of spindle at the metaphase plate

Question 10

Anaphase:

Answer 10

Early Anaphase:
-Centromeres split and daughter chromosomes begin migration to opposite poles

Late Anaphase:
-Two sets of daughter chromosomes approach the poles

Question 11

Telophase:

Answer 11

-Nuclear envelopes begin forming
-Chromosomes begin to become extended and less visible
-Nucleolus reforms, cytokinesis continues

Question 12

Spindle Microtubules:

Answer 12

-Microtubules have two functionally different ends (+/-)
-Made of tubulin subunits, which all face same direction
-Microtubules assembled at centrosomes (- end)
-Microtubule growth and kinetochore attachment occurs at + end
-Microtubules reach the chromosomes when the nuclear envelope breaks down (prometaphase)

Question 13

Types of microtubule:

Answer 13

-Astral microtubules (Form asters at each pole)
-Kinetochore microtubules (Attach to kinetochores)
-Overlap microtubules (Interact with microtubules from opposite pole (also called “polar” microtubules)

Question 14

Kinetochores:

Answer 14

-Attaches paired chromatids to spindle microtubules
-Each chromosome has two kinetochores facing in opposite directions
-Kinetochores associate with specialised nucleosomes (in which H3 is replaced by centromere protein A, CENP-A) at the centromeres

Question 15

Cytokinesis: Animal vs Plant cell

Answer 15

Animal Cell:
-Formation of constriction in middle of cell
-Continues until two daughter cells produced

Plant Cell:
-Only little constriction
-Instead, new cell membrane and cell wall assembled

Question 16

Cytokinesis in animals cells: Cleavage

Answer 16

-Cleavage depends on a belt-like bundle of actin/myosin microfilaments: the contractile ring
-These form during anaphase
-As cleavage progresses the ring tightens around the cytoplasm like a belt

Question 17

Cytokinesis: Animal vs Plant cell

Answer 17

Animal Cell:
-Formation of constriction in middle of cell
-Continues until two daughter cells produced

Plant Cell:
-Only little constriction
-Instead, new cell membrane and cell wall assembled

Question 17

Cytokinesis in plant cells:

Answer 17

-No constriction
-A membrane-enclosed disc, known as the cell plate, forms inside the cell then grows outward, dividing it into two.
-Cell walls can grow after division

Question 18

Cytokinesis: Animal vs Plant cell

Answer 18

Animal Cell:
-Formation of constriction in middle of cell
-Continues until two daughter cells produced

Plant Cell:
-Only little constriction
-Instead, new cell membrane and cell wall assembled

Question 19

Cytokinesis: Animal vs Plant cell

Answer 19

Animal Cell:
-Formation of constriction in middle of cell
-Continues until two daughter cells produced

Plant Cell:
-Only little constriction
-Instead, new cell membrane and cell wall assembled

Question 20

Cytokinesis: Animal vs Plant cell

Answer 20

Animal Cell:
-Formation of constriction in middle of cell
-Continues until two daughter cells produced

Plant Cell:
-Only little constriction
-Instead, new cell membrane and cell wall assembled

Question 21

Cytokinesis: Animal vs Plant cell

Answer 21

Animal Cell:
-Formation of constriction in middle of cell
-Continues until two daughter cells produced

Plant Cell:
-Only little constriction
-Instead, new cell membrane and cell wall assembled

Question 22

Cytokinesis: Animal vs Plant cell

Answer 22

Animal Cell:
-Formation of constriction in middle of cell
-Continues until two daughter cells produced

Plant Cell:
-Only little constriction
-Instead, new cell membrane and cell wall assembled

Question 23

Cytokinesis: Animal vs Plant cell

Answer 23

Animal Cell:
-Formation of constriction in middle of cell
-Continues until two daughter cells produced

Plant Cell:
-Only little constriction
-Instead, new cell membrane and cell wall assembled

Question 24

Cytokinesis: Animal vs Plant cell

Answer 24

Animal Cell:
-Formation of constriction in middle of cell
-Continues until two daughter cells produced

Plant Cell:
-Only little constriction
-Instead, new cell membrane and cell wall assembled

Question 25

Cytokinesis: Animal vs Plant cell

Answer 25

Animal Cell:
-Formation of constriction in middle of cell
-Continues until two daughter cells produced

Plant Cell:
-Only little constriction
-Instead, new cell membrane and cell wall assembled