All cells arise from other cells

Question 1

What is cellular division?

Answer 1

This is a process where eukaryotic cells can produce other cells by a parent cell. However, not all eukaryotic cells can divide, but the ones that can will go through a process called the cell cycle.

Question 2

What are the two types of cell division?

Answer 2

Meiosis and mitosis

Question 3

What is mitosis?

Answer 3

The type of cell division that produces two daughter cells that are identical to the parent cell.

Question 4

What is meosis?

Answer 4

The type of cell division that produces two daughter cells that are not identical to the parent cell, and contain half the amount of genetic material as the parent cell.

Question 5

What are the stages of mitosis ( in order)?

Answer 5

Interphase, G1 phase, S phase, G2 phase.

Question 6

What is the interphase?

Answer 6

This is the stage where biochemical processes occur to prepare for mitosis.

Question 7

What is the G1 phase?

Answer 7

This is when cells grow in size and synthesize proteins mRNA and proteins needed for mitosis.

Question 8

What is the S phase?

Answer 8

The S phase follows the G1 phase and is when the DNA replication occurs. Chromosomes are replicated forming two sister chromatids each.

Question 9

What is the G2 phase?

Answer 9

The G2 phase follows the S phase and is when cells grow and synthesise proteins needed for mitosis. It is during the G2 phase that most microtubules needed for mitosis are produced.

Question 10

How many stages of mitosis are there and how many?

Answer 10

There are 6 stages: Prophase, Prometaphase, Metaphase, Anaphase, Telaphase, and Cytokinesis.

Question 11

What is the prophase stage in mitosis?

Answer 11

Chromosomes condense and become visible
Spindle fibers emerge from the chromosomes
Nuclear envelope breaks down
Centrosomes move toward opposite poles

Question 12

What is the prometaphase?

Answer 12

Chromosomes continue to condense
Kinetochores started to appear at the centrosomes
Mitotic spindle microtubules attach to the kinetochores.

Question 13

What is the metaphase stage?

Answer 13

Chromosomes are lined up at the metaphase plate.
Each sister chromatid is attached to a spindle fiber originating from opposite poles.

Question 14

What is the anaphase stage in mitosis?

Answer 14

Centromeres split in two
Sister chromatids ( now called chromosomes ) are now pulled towards opposite
Certain spindle fibers start to elongate the cell.

Question 15

What is the telaphase stage in mitosis?

Answer 15

Chromosomes arrive at opposite poles and begin to decondense.
Nuclear envelope material surrounds each set of chromosomes.
The mitotic spindle breaks down.
Spindle fibers continue to push poles apart.

Question 16

What is the cytokinesis stage in mitosis?

Answer 16

Animal cells: a cleavage furrow separates the daughter cells.
Plant cells: a cell plate, the precursor to a new cell wall, separates the daughter cell.

Question 17

What are tumor suppressor genes?

Answer 17

Genes that code for proteins to trigger apoptosis ( programmed death of damaged cells/slow cell cycle)

Question 18

What are proto-oncogenes?

Answer 18

Genes that code for proteins to stimulate the cell cycle to progress from one stage to the next.

Question 19

How can mutation to tumor suppressor genes and proto-oncogenes cause cancer?

Answer 19

tumor suppressor: no production of a protein needed to slow a cell cycle.
Proto-oncogenes: form permanently - activated oncogenes.
disruption to cell cycle —- uncontrolled cell division —— tumor.

Question 20

How can cancer treatments control the rate of cell division?

Answer 20

disrupt the cell cycle:
- preventing DNA replication
- disrupt spindle formation = inhibit metaphase / anaphase.
can also damage healthy cells.

Question 21

How do prokaryotic cells replicate?

Answer 21

Binary fission :
1. DNA loop replicates. Both copies stay attached to cell membrane. Plasmids replicate in cytoplasm.
2. Cell elongates, separating the 2 DNA loop.
3. Cell membrane contracts and septum forms.
4. Cell splits into 2 identical progeny cells, each with 1 copy of the DNA loop but a variable number of plasmids.

Question 22

Why are viruses classified as non-living?

Answer 22

They are acellular; no cytoplasm, no metabolism and cannot self-replicate.

Question 23

How do viruses replicate?

Answer 23

1. Attachment proteins attach to receptors on the host cell membrane.
2. Enveloped viruses fuse with cell membranes or move in by endocytosis and release DNA/RNA into the cytoplasm or viruses inject DNA/RNA.
3. Host cell uses viral genetic information to synthesize new viral proteins / nucleic acid.
4. Components of new viral particle assemble.

Question 24

How do new viral particles leave the host cell?

Answer 24

Bud off & use cell membrane to form envelope.
cause lysis of host cell.

Question 25

Why is it so difficult to develop effective treatments against viruses?

Answer 25

Replicate inside living cells = difficult to kill them without killing host cells.