All cells arise from other cells

Question 1

What is a Chromosome?

Answer 1

DNA in coiled form

formed during interphase of cell division (mitosis/meiosis) in Animals/Plants

made of 2 identical/sister chromatids joined by a centromere

carries 2 copies of the same DNA molecule

Question 2

What is a homologous pair of chromosomes?

Answer 2

a pair of chromosomes: 1 maternal (from mother)/1 paternal (from father)

carries same genes but different alleles – there are 23 pairs in humans

Question 3

What is Cell Division?

Answer 3

formation of new cells in multicellular organisms (animals & plants)

2 methods = mitosis & meiosis

mitosis = produces genetically identical cells for growth & repair of tissues

meiosis = produces genetically different haploid cells as gametes for sexual reproduction

Question 4

What does Mitosis (cell cycle) produce?

Answer 4

2 genetically identical cells, diploid (have full set of chromosomes/DNA)

Question 5

Benefit of Mitosis?

Answer 5

growth and repair of tissues

Question 6

Stages of Mitosis?

Answer 6

Interphase/Mitosis/Cytokinesis

Question 7

Interphase?

Answer 7

G1: protein synthesis

S: DNA replication (doubles set of DNA)

G2: organelle synthesis

Question 8

Mitosis

Answer 8

Prophase: DNA coils to form chromosomes, nucleus breaksdown, spindle fibres form

Metaphase: chromosomes line up in middle of cell and attach to spindle fibre via centromere

Anaphase: spindle fibres pull, centromere splits, sister chromatids move to opposite sides

Telophase: chromatids uncoil, nucleus reforms (left with 2 genetically identical nuclei)

Question 9

Cytokinesis

Answer 9

separating cell into 2 (each receives a nucleus and organelles/cytoplasm)

Question 10

What happens to DNA mass in mitosis?

Answer 10

halves

Question 11

What happens to Chromosome number in mitosis?

Answer 11

stays the same (diploid)

Question 12

What is Cancer?

Answer 12

formation of a tumour due to uncontrolled cell division (uncontrolled mitosis)

Question 13

How does uncontrolled cell division occur?

Answer 13

due to mutation of DNA/cells forming cancer cells

mutation can occur randomly or due to mutagens (chemicals/radiation)

cancer cells are rapidly dividing cells (like hair cells, skin cells, red blood cells), they spend

less time in interphase and more time in the other stages (mitosis)

Question 14

Treatment for Cancer?

Answer 14

Surgery = aim is to remove tumour

Chemotherapy =  - using drugs that inhibit mitosis in rapidly dividing cancer cells

			     - problem, also affect normal healthy cells (hair cell, skin cells, rbcs)  	 				           causing side effects (hair loss, dry skin, tiredness)

			     - treatment given as regular doses to allow time for normal healthy 	 			       cells to recover in number

Radiotherapy = radiation used to destroy cancer cells

Question 15

How do Bacteria do Cell Division?

Answer 15

Binary Fission

Copy their DNA (Single Loop and Plasmids) and then separate into 2 new genetically identical bacteria [Asexual Reproduction]