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Biology GCSE Full > Topic 2 - Cell Division and Growth > Flashcards

Topic 2 - Cell Division and Growth Flashcards

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1
Q

What is the cell cycle?

A

● 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

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2
Q

State the three stages of the cell cycle

A

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

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3
Q

What is interphase?

A

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

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4
Q

What does DNA replication involve?

A

● 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

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5
Q

What is a chromosome?

A

A linear DNA molecule tightly coiled around proteins

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6
Q

What happens to chromosomes during DNA

replication?

A

The DNA in the ‘arm’ of each chromosome (chromatid) is replicated.

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7
Q

What is mitosis?

A

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

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8
Q

Why is mitosis important in organisms?

A

● Asexual reproduction
● Growth
● Repair of damaged cells
● Cell replacement

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9
Q

State the four stages of mitosis

A

● Prophase
● Metaphase
● Anaphase
● Telophase

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10
Q

Outline prophase

A

● DNA condenses, chromosomes become visible

● Nuclear membrane disappears

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11
Q

Outline metaphase

A

● Chromosomes line up along the cell equator

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12
Q

Outline anaphase

A

● Spindle fibres attach to each chromosome
● ‘Arms’ of each chromosome pulled to opposite poles
● Chromatids separated

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13
Q

Outline telophase

A

● Nucleus of the cell divides
● New membrane forms around each set of
chromosomes

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14
Q

What does cytokinesis involve?

A

● Division of the cell membrane and cytoplasm
● Two genetically identical ‘daughter’ cells
produced

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15
Q

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

A

10 ÷ 2 = 5
5 cell divisions have taken place
2^5 = 32 cells

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16
Q

What is cancer?

A

● 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

17
Q

What are percentile charts?

A

● 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

18
Q

What does the 95th percentile mean?

A

95% of measurements will be below the value of the 95th percentile

19
Q

What can doctors determine from percentile charts?

A

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

20
Q

Describe growth in animals

A

● 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.

21
Q

Describe growth in plants

A

● 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.

22
Q

What are stem cells?

A

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

23
Q

What is meant by ‘differentiation’?

A

● The process by which stem cells become
specialised (have a specific function)
● Some genes switch on or off, determining cell
type

24
Q

Why is cell differentiation important?

A

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

25
Q

What are embryonic stem cells?

A

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

26
Q

What is the function of embryonic stem cells?

A

Enable the growth and development of tissues in human embryos

27
Q

What are adult stem cells?

A

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

28
Q

What is the primary function of adult

stem cells?

A

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

29
Q

Where are stem cells found in plants?

A

Meristems

30
Q

Where is meristem tissue found?

A

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

31
Q

What are meristematic stem cells?

A

Stem cells found in meristems that are

unspecialised and capable of differentiating into any cell type during the life of a plant

32
Q

How can stem cells be used in medicine?

A

● 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

33
Q

Where can embryonic stem cells be collected from?

A

● Donor stem cells removed from embryos
grown in vitro
● Patient’s own stem cells removed from the
umbilical blood before birth

34
Q

What are the benefits of using stem cells in medicine?

A

● 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

35
Q

What are the risks of stem cell use in medicine?

A

● 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

36
Q

What are the ethical issues related to the

use of stem cells in medicine?

A

● 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

Biology GCSE Full (17 decks)

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