Mitosis

Question 1

Describe histone proteins

Answer 1

1. Globular proteins
2. Organises and condenses DNA tightly so it fits in the nucleus
3. DNA wrapped around 8 histone proteins = nucleosome

Question 2

Describe a chromatid

Answer 2

1. Tightly coiled combination of DNA and proteins
2. Each chromatid contains one DNA molecule supercoiled around 8 histone proteins

Question 3

Describe Telomeres

Answer 3

1. Made of 6 nucleotide sequence
2. Prevents loss of genes
3. Permits continued replication
4. Prevents chromatid ends from fusing
5. Prevents uncoiling

Question 4

Outline the importance of Mitosis

Answer 4

1. Asexual reproduction (cloning)
2. Replacement of damaged/dead cells
3. Repair of tissues
4. Regeneration of body parts
5. Growth

Question 5

Name the 3 parts of the cell cycle

Answer 5

1. Interphase
2. Mitosis
3. Cytokinesis

Question 6

Name the three phases in interphase

Answer 6

1. G1
2. S phase
3. G2

Question 7

State what happens in G1

Answer 7

1. Protein synthesis
2. Increase in cytoplasm volume
3. Growth
4. Production of more organelles
5. Cytoskeleton made

Question 8

State what happens in the S phase

Answer 8

1. Semi conservative DNA replication
2. Synthesis of histone proteins

Question 9

State what happens in the G2 phase

Answer 9

1. Check points, proof reading
2. Increase in energy stores
3. Increase in production of tubulin to make microtubules
4. Cell organelle synthesis

Question 10

Name the 4 phases of mitosis

Answer 10

1. Prophase
2. Metaphase
3. Anaphase
4. Telophase

Question 11

Describe prophase

Answer 11

1. Chromatin condenses and supercoils to form 2 chromatids joined by a centromere
2. Centrioles replicate and start moving to opposite poles
3. Nuclear envelope disappears
4. Nucleolus disappears
5. Spindle begins to form

Question 12

Describe metaphase

Answer 12

1. Nuclear envelope disappears
2. Centriole pairs are at opposite poles
3. Spindle has completely formed
4. Spindle fibres attached to their centromeres of the chromosome
5. Chromosomes continue to condense
6. Chromosomes line up across the equator

Question 13

Describe anaphase

Answer 13

1. Centromeres divide into 2
2. Spindle fibres are attached to centromeres (kinetochores)
3. Spindle fibres contract and shorten to pull the chromatids apart

Question 14

Describe Telophase

Answer 14

1. Sister chromatids reach opposite poles
2. Nuclear envelope reforms
3. Nucleolus reforms
4. Spindle fibres break down
5. Chromatids uncoil to form chromatin

Question 15

Describe cytokinesis

Answer 15

1. Cell divides into two cells
2. Infolding of cell surface membrane
3. Invagination
4. Cleavage furrow forms

Question 16

Suggest where Totipotent cells are produced and what they can differentiate into

Answer 16

1. Found in zygote
2. Can differentiate into ANY cell type

Question 17

Suggest why unipotent stem cells are produced and what they can differentiate into

Answer 17

1. Found in epidermal cells
2. Can differentiate into ONE cell type (Skin cells for skin grafting)

Question 18

Suggest where pluripotent cells are found and what they differentiate into

Answer 18

1. Found in the unbiblical cord and embryo
2. Can differentiate into any cell type apart from embryonic and placental cells

Question 19

Suggest where multipotent cells are found and what they can differentiate into

Answer 19

1. Found in the bone marrow
2. Can differentiate into RBC, WBC, and Platelets

Question 20

Explain how uncontrolled division can result in the formation of a tumour

Answer 20

1. Mutation
2. Oncogene produced
3. Tumour suppressor gene turned off
4. Uncontrolled division leads to formation of a tumour
5. No programmed cell death
6. Benign/malignant
7. Metastasis
8. Telomerase enzymes repeatedly produce telomere sequence