T2 -Cell Division And Growth

Question 1

What is the cell cycle

Answer 1

• a series of events that take place in a cell involving cell growth, DNA replication and cell division
• it is described as the lifecycle of a cell

Question 2

What are the 3 stages of the cell cycle

Answer 2

Stage 1 - interphase
Stage 2 - mitosis
Stage 3 - cytokinesis

Question 3

What is interphase

Answer 3

The longest stage of the cell cycle that involves cell growth, the synthesis of new organelles and DNA replication

Question 4

What does DNA replication involve

Answer 4

• Double helix ‘unzips’ exposing two strands
• DNA bases align next to complementary bases on the DNA strands
• complementary base pairs join
• two identical dna molecules formed

Question 5

What is a chromosome

Answer 5

A linear DNA molecule tightly coiled around proteins

Question 6

What happens to chromosomes during dna replication

Answer 6

The dna in the arm of each chromosome (chromatid) is replicated

Question 7

What is mitosis

Answer 7

A form of cell division that produces two diploid daughter cells, both genetically identical to the parent cell

Question 8

Why is mitosis important in organisms

Answer 8

• asexual reproduction
• growth
• repair of damaged cells
• cell replacement

Question 9

State four stages of mitosis

Answer 9

Prophase
Metaphase
Anaphase
Telophase

Question 10

Outline prophase

Answer 10

• DNA condenses, chromosomes become visible

- nuclear membrane disappears

Question 11

Outline metaphase

Answer 11

Chromosomes line up along the cell equator

Question 12

Outline anaphase

Answer 12

• spindle fibres attach to each chromosome
• arms of each chromosome pulled to opposite poles
• chromatids separated

Question 13

Outline telophase

Answer 13

• nucleus of the cell divides

- new membrane forms around each set of chromosomes

Question 14

What does cytokinesis involve

Answer 14

• Division of the cell membrane and cytoplasm

- 2 genetically identical daughter cells produces

Question 15

A cell divides by mitosis once every 2 minutes. Calculate the number of identical cells present after 10mins

Answer 15

10/2 = 5
5 cell divisions have taken place
2 to the power of 5 = 32

Question 16

What is cancer

Answer 16

• non-communicable disease
• uncontrolled cell division (due to damaged DNA) results in the formation of a primary tumour
• tumour cells break off and spread to other tissues forming secondary tumours

Question 17

What are percentile charts

Answer 17

A chart used to monitor growth

- measurements (e.g foetal length or head circumference) can be compared to the expected values at a certain age

Question 18

What does the 95th percentile mean

Answer 18

95% of measure to will be below the value of the 95th percentile

Question 19

What can doctors determine from percentile charts (3)

Answer 19

• Slower growth than normal (below the bottom line)
• faster growth than normal (above the top line)
• abnormal growth (irregular growth patterns)

Question 20

Describe growth in animals

Answer 20

• cell division occurs in all body cells. It occurs at a slower rate in adults that in younger animals as growth stops and cell division is only required for replacement and repair
• most cells differentiate at an early stage and become specialised. Some adult stem cells retain their ability to differentiate

Question 21

Describe growth in plants

Answer 21

• cell division can only occur in meristematic tissue. The rate of cell division remains the same throughout a plant’s life.
• meristem if stem cells can differentiate into any cell type for as long as the plant lives
• cell elongation occurs in all cells. Cells expand and enlarge enabling growth of the plant

Question 22

What are stem cells

Answer 22

Cells that are unspecialised and capable of differentiating into a range of different cell types

Question 23

What is meant by ‘differentiation’

Answer 23

• the process by which stem cells become specialised (have a specific function)
• some genes switch on or off, determining cell type

Question 24

Why is cell differentiation important

Answer 24

It enables the formation of specialised tissues with specific functions e.g muscle tissue

Question 25

What are embryonic stem cells

Answer 25

Stem cells found in very early embryos that are unspecialised and capable of differentiating into any cell type

Question 26

What is the function of embryonic stem cells

Answer 26

Enable the growth and development of tissues in human embryos

Question 27

What are adult stem cells

Answer 27

Stem cells that can differentiate into a limited range of cell types e.g. bone marrow stem cells

Question 28

What is the primary function of adult stem cells

Answer 28

Replacement of dead cells e.g. replacement of red blood cells which only live for 120 days

Question 29

What are stem cells found in plants

Answer 29

Meristems

Question 30

Where is meristem tissue found

Answer 30

In regions of the plant where cels are continuously dividing e.g root tips, shoot tips

Question 31

What are meristematic stem cells

Answer 31

Stem cells found in meristems that are unspecialised and capable of differentiating into any cell type during the life of a plant

Question 32

How can stem cells be used in medicine

Answer 32

• stem cells collected
• stem cels stimulated to differentiate into specific cell types e.g. heart muscle cells
• specialised cells transplanted into the patient
• used to treat damage or disease e.g. heart disease

Question 33

Where can embryonic stem cells be collected from (2)

Answer 33

• donor stem cells removed from embryos grown in vitro

- patient’s own stem cells removed from the umbilical blood before birth

Question 34

What are the 4 benefits of using stem cells in medicine

Answer 34

• treat damage or disease e.g heart disease, type 1 diabetes
• treat diseases that would otherwise be untreatable
• used in scientific research
• growing organs for transplants

Question 35

What are the risks of stem cell use in medicine (6)

Answer 35

• transplanted stem cells could cause tumours
• finding suitable stem cell donors is a difficult task
• stem cells may be rejected by the body
• potential side effects
• long term risks of using stem cells unknown
• stem cells may become contaminated during preparation and when transplanted transmit infections to the patient, making them sicker

Question 36

What are the ethical issues related to the use of stem cells in medicine (2)

Answer 36

• the embryos that were used to provide stem cells are destroyed which is seen as unethical and a waste of potential human life
• may lead to the reproductive cloning of humans