the cell cycle

Question 1

What are the two main phases of the cell cycle?

Answer 1

Interphase
Mitosis

Question 2

Describe the process of Interphase

Answer 2

Synthesis phase >
DNA replicates semi-conservatively leading to two sister chromatids joined by a centromere
Growth 1 and Growth 2 >
Number of organelles increases
Volume of cytoplasm increases
Protein synthesis
ATP content increased
(order: G1, S, G2)

Question 3

Prophase [5]

Answer 3

• Chromatin coils and condenses, becoming visible under a light microscope
• Appears as two sister chromatids joined by a centromere
• Nuclear envelope breaks down
• Chromosomes free in cytoplasm
• Centrioles move to opposite poles forming spindle
  network

Question 4

What are the 5 stages of Mitosis?

Answer 4

Prophase
Metaphase
Anaphase
Telophase
Cytokinesis

Question 5

Metaphase [2]

Answer 5

• Chromosomes line up along the equator
• Spindle fibres from each pole become attached to the centromeres of the chromosomes

Question 6

Anaphase [5]

Answer 6

• Spindle fibres contract
• Centromere divides
• Pairs of sister chromatids pulled to opposite poles of cell
• Complete set of chromosomes at each pole
• Energy (ATP) required

Question 7

Telophase [4]

Answer 7

• Chromosomes uncoil, becoming longer and thinner
• Chromosomes no longer visible under light microscope
• Spindle fibres and centrioles break down
• Nuclear envelope reforms around each group of nuclei

Question 8

Cytokinesis [2]

Answer 8

• Cytoplasm divides
• Plasma membrane forms around two new genetically identical daughter cells

Question 9

Why is Mitosis necessary? [3]

Answer 9

• Growth of multicellular organisms by increasing cell number
• Repairing damaged tissues / replacing cells
• Asexual reproduction

Question 10

What can uncontrolled cell division lead to?

Answer 10

tumours and cancers

Question 11

What are the two different types of tumour?

Answer 11

Malignant - cancerous, spreads and affects other tissues
Benign - non-cancerous

Question 12

How do prokaryotic cells replicate?

Answer 12

Binary Fission

Question 13

Binary Fission [5]

Answer 13

• Circular DNA and plasmids replicate
• (circular DNA replicates once, plasmids can be replicated many times)
• Cytoplasm expands as each DNA molecule moves to opposite poles of the cell
• Cytoplasm divides
• 2 genetically identical daughter cells, each with a single copy of DNA and a variable number of plasmids

Question 14

Viral Replication [4]

Answer 14

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