topic 2 cells and control

Question 1

What is the cell cycle?

Answer 1

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

Question 2

state the three 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 the new organelles and DNA replication 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?

Answer 8

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

Question 9

State the 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 cell equator

Question 12

outline anaphase

Answer 12

spindle fibres attach to each chromosome and 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

● Two genetically identical ‘daughter’ cells produced

Question 15

what is cancer

Answer 15

uncontrolled cell division results in formation of a tumour (mass of cells)

Question 16

What does the 95th percentile mean?

Answer 16

What does the 95th percentile mean?

Question 17

what are percentile charts?

Answer 17

● A chart used to monitor growth

● Measurements (e.g. fetal length or head circumference) can be compared to the expected values at a certain age

Question 18

What can doctors determine from percentile charts?

Answer 18

● Slower growth than normal (below the bottom line)
● Faster growth than normal (above the top line)
● Abnormal growth (irregular growth patterns)

Question 19

describe growth in animals?

Answer 19

● Cell division occurs in all body cells. It occurs at a slower rate in adults than 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 20

describe growth in plants?

Answer 20

● Cell division can only occur in meristematic tissue. The rate of cell division remains the same throughout a plant’s life.
● Meristematic 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 21

What are stem cells?

Answer 21

unspecialized cells from which differentiated cells develop

Question 22

what is meant by differentiation

Answer 22

● The process by which stem cells become specialised (have a specific function)

Question 23

Why is cell differentiation important?

Answer 23

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

Question 24

What are embryonic stem cells?

Answer 24

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

Question 25

what is the function of embryonic stem cells?

Answer 25

enable the growth and development of tissues in human embryos

Question 26

What are adult stem cells?

Answer 26

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

Question 27

what is the primary function of adult stem cells?

Answer 27

replacement of dead cells

Question 28

Where are stem cells found in plants?

Answer 28

meristems

Question 29

Where is meristem tissue found?

Answer 29

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

Question 30

what are meristematic stem cells?

Answer 30

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

Question 31

How can stem cells be used in medicine?

Answer 31

● Stem cells collected
● Stem cells 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 32

Where can embryonic stem cells be collected from?

Answer 32

● Donor stem cells removed from embryos grown in vitro

● Patient’s own stem cells removed from the umbilical blood before birth

Question 33

what are the benefits of using stem cells in medicine?

Answer 33

● 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 34

what are the risks of stem cell use in medicine

Answer 34

● Transplanted stem cells could cause tumours
● Finding suitable stem cell donors is a difficult task
● Stem cells may be rejected by the body (immunosuppressants taken)
● 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 35

what are the ethical issues related to the use of stem cells?

Answer 35

the embryos that were used to provide stem cells are destroyed which is seen as unethical