3.7->3.8

Question 1

mitosis

Answer 1

produces two daughter cells that have same number of chromosomes as parent cell and each other

Question 2

meiosis

Answer 2

produces four daughter cells
have half of chromosomes as parent cell

Question 3

Prophase

Answer 3

• Chromosomes becomes visible- as thin long threads
• Centrioles(two cylindrical organelles) move to opposite poles of the cell
• Centriole develop spindle fibres(collectively spindle apparatus), which span the cell pole to pole
• The nucleolus disappears
• Nuclear envelope breaks down leaving chromosomes free in the cytoplasm
• The chromosomes are drawn towards the equator or the cell by the spindle fibres

Question 4

Metaphase

Answer 4

• Chromosomes are seen as two chromatids
• Each chromatid is an identical copy of DNA
• Chromatids are by the centromere
• Some microtubules from the poles attach to centromere
• Chromosomes are pulled along by spindle apparatus and arrange themselves around equator of cell

Question 5

Anaphase

Answer 5

• Centromeres divide in two
• Spindle fibres pull individual chromatids apart
• Chromatids move to respective opposite poles and are now referred to as chromosomes
• Energy for this is provided by mitochondria, whihc gather around spindle fibres

Question 6

Telophase

Answer 6

• Chromosomes become longer and thinner
• The disappear altogether, leaving only widely spread chromatin
• Spindle fibres disintegrate
• Nuclear envelope and nucleolus re-form

Question 7

Cytokinesis

Answer 7

Cytoplasm divides between two daughter cells to finish cycle

Question 8

Order of cell division

Answer 8

1. Prophase - Preparation
2. Metaphase - Middle
3. Anaphase - Apart
4. Telophase - two
5. Cytokinesis - Cell splitting

Question 9

Cell division in prokaryotic cells

Answer 9

• Circular DNA molecule replicates and both copies attach to cell membrane
• Plasmids replicate
• Cell membrane begins to grow between two DNA molecules and begins to pinch inward, dividing cytoplasm in two
• New cell wall forms between two molecules of DNA

Question 10

Cell cycle

Answer 10

1. 90% Interphase- most of cell cycle(resting phase)
2. Nuclear division- nucleus divides in two or four
3. Division of cytoplasm(cytokinesis) - cytoplasm divides to produce two new cells(mitosis) or four new cells(meiosis)

overall 24 hours

Question 11

Interphase G1

Answer 11

new cells grows and carries out normal life e.g. Protein synthesis and respiration

Question 12

Interphase S

Answer 12

cell’s DNA is replicated so each chromosome is double stranded
Energy is saved up in the form of ATP

Question 13

Interphase G2

Answer 13

gap where cell checks for and repairs damage to its DNA before proceeding to mitosis

Question 14

Replication of viruses

Answer 14

attach to host cell with attachment proteins on surface
inject nucleic acid into host cell
genetic info on injected viral nucleic acid provides instruction for host cell’s metabolic processes to produce viral components
the new nucleic acid, enzymes and structural proteins are then assembled into new viruses

Question 15

cancer

Answer 15

damaged to genes that regulate mitosis and cell cycle that result in uncontrolled growth and division of mutant cells that are structurally and functionally different from normal cells

a group of abnormal cells(tumor) develops and constantly expands

Question 16

Malignant tumor vs benign

Answer 16

grow more rapidly
less compact
more likely to be life-threatening
travel through body

Question 17

Treatment of cancer

Answer 17

killing dividing cells by blocking part of cell cycle
cell cycle is disrupted and cell division stops

Question 18

Chemotherapy(drugs) function

Answer 18

• preventing DNA from replicating
• inhibiting metaphase stage of mitosis by interfering with spindle formation

Question 19

Problem with drugs

Answer 19

disrupt cell cycle of normal fast dividing cells- explains hair loss