3.2.2 Cell Division

Question 1

DNA in non-dividing cell (+under microscope)

Answer 1

chromatin dispersed throughout the nucleus

-stain as dark blob under a microscope

Question 2

structure of chromosome during mitosis

Answer 2

2 sister chromatids joined together by CENTROMERE

• can be seen by light microscope
• DNA formed into a complex structure by histones (a structural protein)

Question 3

Interphase

Answer 3

-cell carries out normal function
G1: cell grows in size and volume
S: cell organelles synthasised, DNA replicated
G2. growth continues

Question 4

Prophase

Answer 4

-chromosomes condence
-nucleolus disappears and nuclear membrane breaks down
-centrioles spindle fibres develop
(plant cells don’t have centrioles)

Question 5

Metaphase

Answer 5

• chromosomes attach themselves to spindle apparatus

- line up long EQUATOR of cell

Question 6

Anaphase

Answer 6

-spindle fibers contract and pull sister chromotin to opposite poles

Question 7

Telophase

Answer 7

• chromosomes begin to unravel, leaving original chromotin state
• nuclear membrane and nucleus reform, spindle fibers disintergrate

Question 8

Cytokinesis

Answer 8

• parental cell pinched by contractile protien to form 2 daughter cells
• equal distribution of organelles and cytoplasm
• plant cells wall plate forms between 2 cells to separate them

Question 9

How does Cancer occur?

Answer 9

• 1 or both genes (responsible for regulation of mitosis) mutate, causes uncontrolled cell growth
• most mutated cells, but few replicate and form tumours

Question 10

Metastasis

Answer 10

(tumour cells have tendency to seperate)

• malignant tumours invading other religions of body through BLOOD or LYMPH system
• causes secondary tumours

Question 11

Treatment of Cancer

Answer 11

1. ALKYLATING AGENTS-prevent DNA replication in phrophase
2. SPINDLE INHIBATORS at metaphase
   so NO NEW cancer cells formed

Question 12

Causes of Cancer

Answer 12

• radiation (UV)

- carcinogens

Question 13

How do Anti-Cancer drugs affect healthy cells?

Answer 13

• disrupts their cell cycle

- but more effective on rapidly dividing cells

Question 14

Process of Binary Fission

Answer 14

• contains circular DNA and sometimes plasmids
• DNA replicates and attaches to cell membrane
• cell membrane grows from middle and pinches inwards
• new cell wall forms, each daughter cell has single copy of circular DNA

Question 15

Viral nucleic acid

Answer 15

Can be double helix DNA, single helix DNA,
Double helix RNA or single helix RNA

-nucleic acid type depends on virus’s nature and funtion

Question 16

How viruses replicate

Answer 16

• ATTACHES to cell by protiens
• INJECTS its nucleic acid into cell
• nucleic acid INSTRUCTS host cell to produce viral DNA
• viral components SYNTHESISED
• selfASSEMBLE inside cell
• cell ruptures, RELEASING new mature viral cells