All cells arise from other cells

Question 1

Interphase

Answer 1

S phase: DNA replicates semi-conservatively leading to two sister chromatids

G1 and G2: Number of organelles and volume of cytoplasm increases; protein synthesis occurs, ATP content increased

Question 2

Prophase

Answer 2

Chromosomes condense, becoming shorter and thicker and appear as two sister chromatids joined by a centromere

Nuclear envelope breaks down and centrioles move to opposite poles forming spindle network

Question 3

Metaphase

Answer 3

Chromosomes align along equator

Spindle fibres attach to chromosomes by centromeres

Question 4

Anaphase

Answer 4

Spindle fibres contract, pulling sister chromatids to opposite poles of the cell

Centromere divides

Question 5

Telophase

Answer 5

Chromosomes uncoil, becoming longer and thinner

Nuclear envelope reforms, resulting in two nuclei

Spindle fibres and centrioles break down

Question 6

Cytokinesis

Answer 6

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

Question 7

Importance of mitosis

Answer 7

Growth of multicellular organisms by increasing cell number

Repairing damaged tissues/replacing cells

Asexual reproduction

Question 8

Uncontrolled cell division

Answer 8

Can lead to the formation of tumours and cancer

Malignant tumour: spreads and affects other tissues/organs

Benign tumour: non-cancerous

Question 9

Cancer treatments

Answer 9

Aimed at controlling the rate of cell division

Disrupt the cell cycle: cell division/mitosis slows, tumour growth slows

Prevent DNA replication: prevent/slows down mitosis

Disrupts spindle activity formation, chromosomes can’t attach to spindle by their centromere and sister chromatids can’t be pulled to opposite poles of the cells, prevents/slows mitosis.

Question 10

Cancer treatment advantage and disadvantage

Answer 10

Disadvantage: Disrupt cell cycle of normal cells too, especially rapidly dividing ones e.g. cells in hair follicles

Advantage: Drugs more effective against cancer cells because dividing uncontrollably/rapidly

Question 11

Binary fission

Answer 11

Circular DNA and plasmids replicate (circular DNA replicates once, plasmids can be replicated many times)

Cytoplasm expands (cell gets bigger) as each DNA molecule moves to opposite poles of the cell

Cytoplasm divides

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

Question 12

Viral replication

Answer 12

Attachment protein binds to complementary receptor protein on surface of host cell

Inject nucleic acid (DNA/RNA) into host cell

Infected host cell replicates the virus particles