8b Mitosis and cancer

Question 1

phase of the cell cycle

Answer 1

1. G1 : cells prepare for DNA replication – cells grow, respire and new proteins and organelles are produced.
2. S : DNA replication occurs
3. G2 : a relatively short gap before mitosis – cell grows and prepares for mitosis
4. M : mitosis

Question 2

Interphase

Answer 2

What happens to the DNA during interphase?
- Replicates

What other events occur during interphase?
- Protein synthesis Increase in number of organelles ATP production (respiration)

Question 3

Prophase

Answer 3

What happens to the chromosomes during prophase?
- Condense/shorten (due to coiling up of DNA) & become visible

What is the function of the centromere?
- Holds 2 chromatids together

What happens to the nuclear membrane at the end of prophase? — Breaks down

Question 4

Metaphase

Answer 4

What happens to the chromosomes during metaphase?
- Line up along equator of cell & each attaches to an individual spindle fibre by its centromere

Question 5

Anaphase

Answer 5

What happens to the chromosomes during anaphase?
- Centromere divides, spindle fibres contract pulling apart the chromatids of each chromosome. Sister chromatids go to opposite poles.

Question 6

Telophase

Answer 6

What happens to the chromosomes during telophase?
- Uncoil and become threadlike again, no longer visible

What forms around each set of daughter chromosomes?
- New nuclear membrane/envelope

Question 7

Cytokinesis

Answer 7

· Division of the cytoplasm usually follows mitosis fairly quickly.

· Cells without a cell wall just pinch themselves in two and a membrane forms in the middle of the cell. Eventually, the cell membrane from one side of the cell joins that from the opposite side of the cell and the two new daughter cells separate.

· Cells with a cell wall cannot pinch themselves in two. Instead a new cell wall forms in the middle of the cell.

Question 8

mitotic index

Answer 8

Mitotic index = number of cells undergoing mitosis /
Total number of cells

It can be expressed as a percentage (simply multiply by 100).

Question 9

Divison of Prokaryotic cell

Answer 9

binary fission

· Replication of the circular DNA, including the plasmids

· The cell membrane begins to grow between the two main DNA loops and begins to pinch inward, dividing the cytoplasm into two.

· A new cell wall forms between the two DNA loops, forming two daughter cells, each with a copy of the main DNA loop and a variable number of copies of plasmids

Question 10

divison of viruses

Answer 10

non-living, do not undergo cell division.

· Instead they replicate by attaching to a host cell using the attachment proteins on their surface.

· They then inject their nucleic acid into the host cell, which is then used to produce viral components (i.e. proteins) that are then assembled into new viruses.