Cell division 1.6

Question 1

State the function of mitosis.

Answer 1

to produce two daughter cells identical to the parent cell

Question 2

List processes which involve mitosis.

Answer 2

Tissue repair (for example after injury)
Growth of the organism
Embryonic and fetal development
Replacement of cells that die naturally
Asexual reproduction via cloning
Maximizing the cell SA:V ratio surface area to volume

Question 3

What are the names of the four phases of mitosis?

Answer 3

Prophase, metaphase, anaphase and telophase

Question 4

Draw typical eukaryotic cells as they would appear during the four phases of mitosis.

Answer 4

see notion

Question 5

Outline four events that occur during prophase.

Answer 5

Nuclear membrane breaks down and nucleus dissolves
DNA supercoils and chromosomes condense
Chromosomes are comprised of genetically identical sister chromatids (they are joined at centromere)
mitotic spindle begins to develop. The mitotic spindle are proteins that move the chromosomes around the cell.

Question 6

Outline the process of metaphase.

Answer 6

Microtubule spindle fibres from both centrosomes connect to the centromere of each chromosome helps align chromosomes along the equatorial plane of the cell (the centre)

Question 7

Outline the process of anaphase.

Answer 7

Microtubules attached to the chromosomes contract, which pulls the daughter chromosomes apart and toward opposite poles of the cell.
The centromeres of each pair of sister chromatids separate, creating two daughter chromosomes.

Question 8

What are four events that occur in the telophase?

Answer 8

Nuclear membrane reforms around each set of daughter chromosomes.
Chromosomes uncoil to form chromatin.
The spindle fibers are broken down and “disappear.”
Occurs simultaneously as cytokinesis.

Question 9

Explain why chromosomes must condense during mitosis.

Answer 9

so that it can more easily be moved to the poles of hte cell without getting tangled and/or broken

Question 10

Describe the structure of a replicated chromosome, include the centromere and sister chromatids.

Answer 10

each chromosome is seen as a pair of sister chromatids joined a the centromere.

Question 11

Define cytokinesis.

Answer 11

division of the cytoplasm and organelles into two daughter cells

Question 12

Describe the formation of the cleavage furrow in animal cell cytokinesis.

Answer 12

• microfilaments located beneath the plasma membrane at the equator pulls the plasma membrane inward.
• The inward pull on the plasma membrane produces the characteristic cleavage furrow.
• When the cleavage furrow reaches the centre of the cells, it is pinched apart to form two daughter cells.

Question 13

Describe the formation of the middle lamella and cell wall in plant cell cytokinesis.

Answer 13

Golgi apparatus forms vesicles that consist of material to build a new cell wall.
Vesicles merge and form the cell plate.
The cell plate grows and divides into two daughter cells.

Question 14

Outline events of G1, S, G2 and G0 phases of interphase.

Answer 14

G1:
protein synthesis takes place -> cell growth sizewise.
Proteins required for DNA synthesis (the next phase) are made.
Mitochondria and chloroplasts are replicated.

S:
DNA replication takes place. Mitochondria/ chloroplasts are replicated.

G2:
cell is actively preparing for cell division.
Protein synthesis occurs to produce the proteins needed for cell division, such as microtubule proteins that will make up a mitotic spindle.

Question 15

Explain the role of cyclin and cyclin-CDK complexes in controlling the cell cycle.

Answer 15

Cyclins are proteins that control the progression of the cell cycle.
- bind to enzymes called cyclin-dependent kinases (CDKs) and activate them.
activated CDKs attach phosphate groups (phosphorylation) to other proteins in the cell.
triggers other proteins to become active and carry out tasks; in this case, specific to the phases of the cell cycle.

Question 16

State the role of cyclins D, B, A and E in the cell cycle.

Answer 16

Cyclin D: synth- during early G1 -> conc. high enough triggers transition to S phase.
Cyclin E: synth. midway through G1 + peaks in S phase -> triggers preperation for DNA replication
Cyclin A: synth. in S phase - initatiates DNA replication + ensures its only done once. In G2-> triggers mitosis
Cyclin B: triggers entry into prophase, peaks at metaphase but for ananphase to start, B must decrease

Question 17

draw the cyclin graph

Answer 17

see notion

Question 18

Define tumor, benign, malignant, metastasis, cancer

Answer 18

primary tumor: benign (do not move around the body, non cancerous) or malignant (spread around body via metastasis, cancerous)
metastasis: malignant tumor spreads through body via blood to another location(s)
secondary tumors: found in multiple locations.

Question 19

Describe how cancer arises,

Answer 19

dysregulation of the cell cycle resluts in unregulated cell diviosn which forms tumors. tumors can cause cancers if they spread via metastasis

Question 20

Explain the relationship between oncogenes, tumor suppressor genes and cancer.

Answer 20

pronto oncogenes: genes that code for proteins that regulate the cell cycle
onco genes: are the mutated forms of pronto onco genes which cause cancer.
mutagens: any factors that can result in the mutation of pronto-onco genes into oncogenes
carcinogens: mutagens that can cause cancer.

Question 21

State the formula for calculation of a mitotic index.

Answer 21

divide the number of cells in mitosis by the total number of cells observed. Multiply the result by 100 to get the Mitotic Index as a percentage

Question 22

Outline the use of mitotic index calculations in diagnosis and treatment of cancer.

Answer 22

the higher the M.I relative to a tissue specific standard M.I, the more likely the tissue is cancerous.
can test effectiveness of treatment with M.I