2.2 mitosis

Question 1

Cell cycle

Answer 1

In multicellular organisms, not all cells retain their ability to divide

Eukaryotic cells that do retain the ability to divide show a cell cycle

Question 2

Interphase

Answer 2

S phase - DNA replicates semi-conservatively leading to 2 sister chromatids

G1 and G2 - number of organelles and volume of cytoplasm increases, protein synthesis , ATP content increased.

Question 3

Mitosis

Answer 3

Parent cell divides = 2 genetically identical daughter cells, containing identical copies of DNA of the parent cell

PMAT

Question 4

Prophase

Answer 4

Chromosomes condense

Centrosomes move to opposite poles of the cell and form spindle fibres

Nuclear membrane breaks down

Nucleolus dissolves

Question 5

Metaphase

Answer 5

Chromosomes become attached to the spindle fibres by their centrosomes

Align at the centre of the cell

Question 6

Anaphase

Answer 6

Centromeres divide, separating each pair of sister chromatids

The spindle fibres contract, pulling the chromatids to opposite poles of the cell via their centromeres

Question 7

Telophase

Answer 7

Once the chromosomes are set at the poles, spindle fibres dissolve

Chromosomes decondense

Nuclear membranes reform around each chromosomes set

Cytokinesis occurs, splitting the cell into 2

Question 8

Cytokinesis

Answer 8

The division of the cytoplasm, usually occurs, producing 2 new cells

Question 9

Parent cell divides

Answer 9

To produce 2 genetically identical daughter cells for

• growth of multicellular organisms by increasing cell number
• repairing damaged tissues/replacing cells
• asexual reproduction

Question 10

Uncontrolled cell division

Answer 10

Leads to formation of tumours and cancers

Malignant tumour - cancer, spreads and affects other tissues/organs

Benign tumour - non-cancerous

Question 11

Cancer treatments

Answer 11

Disrupt cell cycle - as cell division slows - tumour growth slows

• prevent DNA replication >prevent mitosis
• disrupt spindle formation > chromosomes cannot attach to spindle by their centromeres > sister chromatids cannot be pulled to opposite poles of the cells > prevent mitosis

Question 12

Adv/dis of cancer cells

Answer 12

Disrupts cell cycle of normal cells too, especially rapidly dividing ones (hair follicles)

Drugs more effective against cancer cells as they’re dividing uncontrollably

Question 13

Binary fission

Answer 13

circular DNA and plasmids replicate

Cytoplasm expands as each DNA molecules moves to opposite poles of the cell

Cytoplasm divides

2 daughter cells produced, each with a single copy of DNA and a variable number of plasmids

Question 14

Viral replication

Answer 14

Viruses don’t undergo cell division as they are non-living

1. Attachment protein binds to complementary receptor protein on surface of host cell
2. Inject nucleic acid (DNA/RNA) into host cell
3. Infected host cell replicates the virus particles

Question 15

Actual size =

Answer 15

Size of image / magnification

Question 16

Mitotic index

Answer 16

= number of cells in mitosis / number of cells