Cell Division

Question 1

Name the phases of mitosis

Answer 1

G1 interphase from 1/2 o’clock to 5/7 o’clock
S 5/8 to 9 o’clock
G2 9 to 11 o’clock
Mitosis (nuclear division) 11to 12 o’clock

Question 2

What happens In G1 phase of mitosis

Answer 2

Organelles are synthesized and biochemicals produced, cell leaves cell cycle
G1 checkpoint checks for cell size

Question 3

What happens during the S phase of mitosis

Answer 3

Synthesis phase- dna is replicated by semi-conservative replication

Question 4

What happens during G2 phase of mitosis

Answer 4

Second growth phase- energy stores are increased, make new organelles, G2 checkpoint checks for dna replication

Question 5

What phases are there during mitosis/ nuclear division phase

Answer 5

Prophase: chromosomes become visible, shorten and thicken. Spindle develops. Nuclear envelope disintegrates

Metaphase: chromosomes are arranged on the equator

Anaphase: chromosomes migrate to opposite poles

Telophase: spindle disintegrates, nuclear envelope develops

Cell divisions 1 to 2 o’clock: cell divides by construction in animal cells and cell plate formation in plants

Question 6

What do cycling and cyclin-dependent kimases do

Answer 6

Control the checkpoints (G1 and G2)

Question 7

State what is produced during
A: the g1 phase of interphase
B: the S phase of interphase (3 marks)

Answer 7

A: Organelles [1] (named) biochemicals [1]
B: DNA[1]

Question 8

Explain the importance of checkpoints during cell cycle (3 marks)

Answer 8

The timing of each step in cell cycle is crucial [1] checkpoints regulate sequence of events in the cycle [1] the cycle will be halted if errors are detected [1]

Question 9

How many daughter cells do mitosis produce and are they identical

Answer 9

2 identical daughter cells

Question 10

Why are genetically identical cells important

Answer 10

Growth
Repair (of damaged cells)
Replacement (of cells, eg RBC, that have limited lifespans)
Asexual reproduction (in eukaryotes)

Question 11

Describe the interphase of mitosis

Answer 11

Dna replicates, has 2 copies of all its genetic material

One chromosome, 1 chromatid (before replication)
1 chromosome, 2 chromatids (after replication)

Chromatic held by centromere

Question 12

Describe the prophase of mitosis

Answer 12

Chromatin (comprising of DNA and histone proteins) condenses, chromosomes become visible
Nucleolus disappears
Centrioles move to the poles of the cell
Nuclear envelope break down (towards end of prophase)

Question 13

Describe what happens during the metaphase of mitosis

Answer 13

Spindle Fibres (organized by centrioles) attach to centromeres (towards end of prophase/start of metaphase)
Chromosomes line up along the center (equator) of the cell

Question 14

Describe what happens in the anaphase of mitosis

Answer 14

Spindle Fibres shorten
Centromeres divide
Chromatids are separated and pulled to opposite poles of the cell

Question 15

Describe what happens during the telophase of mitosis

Answer 15

Chromatids are at the poles if the cell (can be referred to as daughter chromosome)
Nuclear envelope reform around each set of chromosomes
Chromosomes uncoil (and no longer visible)
Cell division (cytokinesis) begins

Question 16

What happens during cytokinesis

Answer 16

Division of a cell
Begins in telophase, results in 2 genetically identical cells, each receives half of organelles and cytoplasm

Question 17

What happens in animals and plants during cytokinesis

Answer 17

Animals: a cleavage forms (ie cell surface membrane pulled together by cytoskeleton)

Plants: cell wall prevent cleavage furrows, 2 identical daughter cells separated by new cell wall production down center of original cell

Question 18

What is the order of stages In meiosis

Answer 18

Prophase 1
Metaphase 1
Anaphase 1
Telophase 1
Prophase 2
Metaphase 2
Anaphase 2
Telophase 2

Question 19

What happens during prophase metaphase anaphase and telophase 1

Answer 19

Prophase 1: nuclear envelope disintegrates, spindles form, chromosome condense. Homologous chromosomes pair up, crossing over

Metaphase 1: homologous pairs (bivalents) line up at cell equator, independent assortment of chromosomes

Anaphase 1: homologous chromosome pairs are separated- sister chromatid both remain attached to centromeres

Telophase 1: chromosomes assemble at either pole. Cytokinesis- 2 haploid cells formed

Question 20

What happens during meiosis II

Answer 20

Prophase 2: chromosomes condense, nuclear envelope breaks down, spindle forms

Metaphase 2: chromosomes line up at equator. Independent assortment of chromatids

Anaphase 2: random segregation of chromatids

Telophase 2: chromatids assemble at poles. Cytokinesis- 4 haploid daughter cells formed