Chapter 6 - Cell division

Question 1

What is a cell cycle ?

Answer 1

Highly ordered sequence of events leading to division of the cell into identical daughter cells

Question 2

What are the two phases of the cell cycle ?

Answer 2

1) Interphase
2) Mitotic phase

Question 3

What is the interphase ?

Answer 3

Phase of periods of growth, where cells are not actively dividing

Question 4

What occurs at interphase ?

Answer 4

• DNA is replicated and checked for errors
• Protein synthesis occurs
• Mitochondria grow and divide in plant and algal cytoplasms

Question 5

What are the stages interphase is split into ?

Answer 5

G1 stage
S stage
G2 stage

Question 6

What occurs at each stage of interphase ?

Answer 6

G1 - First growth phase
Proteins are synthesised
Cells increase in size
S - DNA is replicated within nucleus
G2 - Cells continously increase in size
Energy source is increased and duplicated
DNA is checked for errors

Question 7

What are the different checkpoints at interphase ?
Where are they located ?

Answer 7

G1 checkpoint - After G1 phase
G2 checkpoint - After G2 phase
Metaphase checkpoint - During metaphase

Question 8

What does the G1 checkpoint check ?

Answer 8

• Cell size
• Nutrients
• Growth factors
• DNA damage

Question 9

What does the G2 checkpoint check ?

Answer 9

• DNA replication has any errors
• Cell size
• DNA damage

Question 10

What does the metaphase checkpoint check ?

Answer 10

• Chromosomes are attached to spindle fibres
• Mitosis can continue to occur without this checkpoint

Question 11

What is the mitotic phase ?

Answer 11

• Period of cell division
• Mitosis and cytokenisis occur

Question 12

What is the mitotic phase needed for ?

Answer 12

• Asexual reproduction
• Growth
• Repair
• Replacement of tissue

Question 13

What must occur before the Mitotic phase ?

Answer 13

Replication of DNA i.e. Interphase

Question 14

What are the four stages of mitosis ?

Answer 14

(I) - [Interphase]
Party - Prophase
More - Metaphase
At - Anaphase
The - Telophase
Club - Cytokenisis

Question 15

What occurs at the prophase ?

Answer 15

• Chromatin fibres coil and condense to form chromosomes
• Nucleur membrane begins to break down
• Microtubules form spindle fibres linking poles
• Spindle fibres move chromatic
• Centrioles migrate to either ends of the cell
• Nucleur envelope disintegrates

Question 16

What occurs at metaphase ?

Answer 16

• Chromosomes are held in metaphase plate by spindle fibres

Question 17

What occurs at anaphase ?

Answer 17

• Centromeres divide
• Chromosomes are pulled to opposite poles and are separated

Question 18

What occurs at telophase ?

Answer 18

• Chromatids have reached the poles
• Nucleur envelope reforms
• Chromsomes uncoil and nucleuolus is formed

Question 19

How does cytokenisis occur within animals cells ?

Answer 19

• Cleavage furrow forms in the middle of the cell
• Cell surface membrane is pulled inwards by cytoskeleton

Question 20

How does cytokenisis occur in plant cells ?

Answer 20

• Due to the cell wall no cleavage furrow can form
• Golgi apparatus forms vesicles where metaphase plate is located
• Vesicles then fuse with eachother and with cell wall

Question 21

What does mitosis result in ?

Answer 21

Formation of 2 identical diploid cells

Question 22

What does meiosis result in ?

Answer 22

• Nucleus divides twiceand contains a haploid number of parent cells hence meiosis is known as reduction division

Question 23

How does meiosis occur ?

Answer 23

Split into Meiosis I and Meiosis II

Question 24

What occurs in Meiosis I that is different to Mitosis ?

Answer 24

Prophase I
- Homologous pairs of chromosomes are formed which leads to Bivalence
Metaphase I
- Orientation of Chromosomes are random which leads to random assortment
Anaphase I
- Sections of DNA are broken off and rejoin to the other chromosome strand at the chiasmata
- Recombinant chromosomes are formed
Telophase I
- Same as in Mitosis

Question 25

What occurs in Meiosis II that is different to Mitosis ?

Answer 25

Each stage is the same

Question 26

What are tissues ?

Answer 26

Collection of differented cells

Question 27

What are specialised cells ?

Answer 27

Differentiated cells that have a specific function

Question 28

What are the main specialised cells in animals ?
How are they specialised ?

Answer 28

1 - Erythrocytes
- Biconcave shape (Increases SA:V)
- No nuclei (More space for Haem)
- Flexible
2 - Neutrophils
- Multilobed nucleus (Easier to squeeze through small gaps)
- Granular cytoplasm
3 - Sperm cells
- Flagellum
- Lots of mitochondria
- Acrosome (Digestive enzyme to eat through protective layer on ovum)

Question 29

What are the specialised cells in plants ?
How are they specialised ?

Answer 29

1 - Palisade
- Contain lots of chloroplast
- Closely packed
- Thin cell walls
- Large Vacuole (maintains turgor pressure)
2 - Root hair cells
- Long extentions (Increases SA:V)

Question 30

What are the specialised tissues in animal cells ?

Answer 30

1 - Squamous epithelium
2 - Ciliated epithelium
3 - Cartilage
4 - Muscle
5 - Goblet cells

Question 31

What are the specialised tissues in plant cells ?

Answer 31

• Epidermis
• Xylem tissues
• Phloem tissues
• Organs

Question 32

What are stem cells ?

Answer 32

Undifferentiated cells that are not adapted to any function
Have the ability to be specialised

Question 33

What are the potencies of stem cells ?

Answer 33

1 - Totipotent (Differentiate into anything)
2 - Pluripotent (Form whole tissues and not organisms)
3 - Multipotent (Form a range of cells)

Question 34

What are the main sources of animal stem cells ?

Answer 34

1 - Embryonic stem cells (Totipotent)
2 - Adult tissue stem cells (Multipotent)