17) Unit 1 - The Cell Cycle

Question 1

Purpose of the cell cycle in multicellular organisms

Answer 1

For growth and repair - to replace dead cells and repair tissues

Question 2

What is the purpose of the cell cycle in unicellular organisms

Answer 2

mode of reproduction

Question 3

Describe the process of the cell cycle in unicellular organisms

Answer 3

1) replication of singular circular DNA chromosome
2) cell growth
3) ingrowth of plasma membrane
4) cell division (fission)
5) repeats approx every 20 minutes in bacteria

Question 4

what stages does the cell cycle consist of in multicellular organisms

Answer 4

• Interphase (G1, S, G2)

* M Phase

Question 5

what happens in G1, S, G2

Answer 5

G1: initial phase of growth
(e.g.making proteins which are what the organelles are made of, making DNA polymerase for the duplication of DNA is S phase)

S: Replication of DNA

G2: Second Growth Phase

Question 6

name and describe 2 process that occur during the M phase

Answer 6

Mitosis:
separation and segregation of replicated chromosome and the formation of daughter nuclei by the division of the nucleus

Cytokinesis:
Division of the cytoplasm into two daughter cells

Question 7

List the 4 stages of mitosis

Answer 7

• Prophase
• Metaphase
• Anaphase
• Telophase

Question 8

describe prophase

3 pts

Answer 8

• chromatin starts to condense to chromosomes
• they appear as pairs of identical chromatids
• in the cytoplasm, the spindle fibres start to form at the 2 centrosomes

Question 9

describe metaphase

3 pts

Answer 9

• Chromosomes line up at the equator of the cell. This position is called the metaphase plate
• Spindle fibers extend from each pole and attach to each sister chromatid
• The spindle fibers attach to each chromatid at a point called the kinetochore

Question 10

describe anaphase

3 pts

Answer 10

• Proteins holding the sister chromatids together degrade
• sister chromatids are separated and know as daughter chromosomes
• Spindle fibers attached to each daughter chromosome shorten and pull them to opposite poles of the cell

Question 11

Describe telophase:

3 pts

Answer 11

• cell lengthens and a nuclear membrane forms around each set of chromosomes
• chromosomes begins to uncoil
• Cytokinesis occurs during this phase and the cytoplasm separates into two daughter cells

Question 12

describe the process of cytokinesis in animal cells

Answer 12

1) achieved by the action of a contractile ring of structural proteins (actin and myosin)
2) the cytoskeleton contracts from inside the cell and when it meets it cleaves
3) always symmetrical

Question 13

process of cytokinesis in plants

Answer 13

differs as they have a cell wall

1) the cytoplasm is sectioned off by the formation of a new cell wall (cell plate)
2) the formation of the cell wall is guided by the remains of the spindle fibers which push the cell plate to the center of the cell
3) cell splits when it fuses and releases cellulose
4) division can be symmetrical or asymmetrical

Question 14

What is the role of spindle fibers in mitosis

Answer 14

Spindle fibers allows:

• the alignment of chromosomes in metaphase
• separation of daughter chromosomes to opposite poles
• formation of daughter nuclei as chromosomes have been group at opposite poles

Question 15

how to calculate mitotic index

Answer 15

(number of cells undergoing mitosis/ total number of cells) *100

Question 16

what happens when there is an:

1) underproduction of the cell cycle?
2) overproduction of the cell cycle?

Answer 16

1) degenerative diseases like Alzheimer’s

2) Tumour formation