Chapter 4: The Cell Cycle

Question 1

What is the purpose of cell replication?

Answer 1

It is essential for growth, repair and maintenance, and reproduction.

Question 2

What is binary fission?

Answer 2

Binary fission is the method of reproduction bacteria use.

Question 3

How does binary fission occur?

Answer 3

Its similar to mitosis as it is cell division but they have different purposes.

Question 4

What is the purpose of binary fission in comparison to mitosis?

Answer 4

Binary fission is a way for bacteria to reproduce and increase population whereas mitosis is to replace old, worn-out cells and to increase the size of an organism.

Question 5

Cytokinesis definition

Answer 5

Cytokinesis is when the cells enlarges in preparation for the division to be able to survive.

Question 6

What does mitosis do?

Answer 6

Mitosis ensures that each cell is an exact replicate (daughter cell) prior to cytoplasmic division (cytokinesis).

Question 7

What is the stage in between nuclear divisions (M)?

Answer 7

Interphase

Question 8

What are the periods in interphase?

Answer 8

Active Growth (G1)
Synthesis of DNA (S)
Preparation for the next division (G2)

Question 9

Order of periods in Interphase

Answer 9

G1, S, G2, M

Question 10

What is G0?

Answer 10

G0 is an extended G1 phase which occurs in cells that have reached maturity and no longer need to replicate. This usually occurs in specialised cells.

Question 11

G1 phase

Answer 11

The cell produces proteins, grows and carries out its usual tasks for the body

Question 12

S phase

Answer 12

Exact duplicates of DNA are formed

Question 13

G2 phase

Answer 13

Preparation for cell division

Question 14

M phase

Answer 14

The cell divides into two daughter cells (mitosis)

Question 15

What are the 4 stages of mitosis?

Answer 15

Prophase
Metaphase
Anaphase
Telophase

Question 16

Prophase

Answer 16

Prophase is considered to be the first true stage of the mitotic process.
- The chromatin threads condense and become a visible pair of chromatids held together by the centromere.
- Centrioles then move to either end of the cell and microtubules begin to radiate from them.
- This then begins to form the framework for fibres as the nuclear membrane breaks down.

Question 17

Metaphase

Answer 17

The chromatid pairs move along the metaphase plate towards the centre of the cell.
The centromere of each pair is attached to a spindle fibre.

Question 18

Anaphase

Answer 18

The spindle fibres attached to the chromatids begin to pull them apart. They move to opposite poles of the cell and are now called chromosomes as they are now individual.

Question 19

Telophase

Answer 19

• The two sets of chromosomes form tight clusters at either side of the cell.
• The chromosomes decondense as the chromatin unwinds and become less visible.
• A new nuclear envelope forms, nucleoli reforms and the spindle disassembles.

Question 20

Apoptosis

Answer 20

The process for a cell to
self-destruct when necessary such as, structural damage, worn-out or internal altercations.

Question 21

What is the process of apoptosis?

Answer 21

• Shrink and develop bubble-like protrusions on their surface
• The DNA breaks down as well as some organelles
• The entire cell splits into small fragments
• The chunks release signals that attract debris-eating immune cells

Question 22

What is necrosis?

Answer 22

Necrosis is essentially when a cell “spills their guts” due to plasma membrane damages

Question 23

Extrinsic apoptosis

Answer 23

This begins outside the cell when conditions in the extracellular environment determine the cell must die

Question 24

Intrinsic apoptosis

Answer 24

This is a result of internal damages of a cell that cause stress activating the apoptotic pathway

Question 25

What is a checkpoint?

Answer 25

A checkpoint is used to determine if a cell is ready to move into the next stage of the cell cycle

Question 26

G1 Checkpoint

Answer 26

The cell can only pass onto the S phase if it is of adequate size and appropriate energy reserves. This phase is signalled by cyclins and cyclin dependent kinases

Question 27

G2 Checkpoint

Answer 27

The G2 checkpoint's most important role is to ensure the chromosome has been exactly replicated. When an issue is identified, the cell tries to repair it but when the cell is deemed okay it moves onto the mitotic phase

Question 28

M checkpoint

Answer 28

This occurs at the end of the metaphase cycle where the cell is checked based on how the sister chromatids are attached to the spindles as the cell is ready to divide

Question 29

Proto-oncogenes

Answer 29

Code for proteins to stimulate cell division, prevent cell differentiation and regulate programmed cell death

Question 30

Tumour suppressor genes

Answer 30

This keeps the cell from dividing too quickly and allows repairs to the cell to occur and also tell cells when to die

Question 31

p53 gene

Answer 31

This prevents tumours and codes for a protein that regulates the cell cycle

Question 32

What signals may trigger p53 proteins? What are there major functions?

Answer 32

Internal damages may cause more p53 proteins which function growth arrest, DNA repair and apoptosis

Question 33

Mutagens

Answer 33

A substance that affects an organism's genetic system by altering hereditary materials

Question 34

Are mutagens biological, physical or chemical?

Answer 34

All

Question 35

What are chemical mutagens?

Answer 35

They alter DNA, by interrupting its structure, sequence or replication

Question 36

Physical mutagens

Answer 36

UV light, nuclear radiation and X-rays are examples of physical mutagens which also alter DNA

Question 37

What are biological mutagens?

Answer 37

These are viruses that impair cell cycle regulation, ultimately resulting in cancer

Question 38

Stem cells

Answer 38

They are unspecialised cells that have the potential to become specialised cells

Question 39

Totipotent stem cells

Answer 39

Can differentiate between all tissue types

Question 40

Pluripotent stem cells

Answer 40

They are able to differentiate between most types of tissues but they are unable to produce all tissues of the body

Question 41

Multipotent stem cells

Answer 41

Able to differentiate into a number of tissues