CGE: Stem Cells

Question 1

Totipotent stem cells

Answer 1

Can mature into any type of body cell.

Question 2

All specialised cells come from what?

Answer 2

Stem cells

Question 3

Where can stem cells be found?

Answer 3

In the embryo and in some adult tissues.

Question 4

Where are totipotent stem cells present?

Answer 4

Only present in mammals in the first few cell divisions of an embryo.

Question 5

What happens to totipotent stem cells in mammals after the first few cell divisions?

Answer 5

They become pluripotent.

Can still specialise into any cell in the body, but lose the ability to become cells that make up the placenta.

Question 6

Stem cells in adult mammals are either…

Answer 6

Multipotent or unipotent

Question 7

Pluripotent stem cells

Answer 7

Stem cells that can specialise into any body cell, but have lost the ability to differentiate into cells that make up the placenta.

Question 8

Multipotent stem cells

Answer 8

Stem cells that can differentiate into a few different types of cell.

Question 9

Unipotent stem cells

Answer 9

Stem cells that can only differentiate into one type of cell.

Question 10

Can mature into any type of body cell.

Answer 10

Totipotent stem cells

Question 11

Stem cells that can specialise into any body cell, but have lost the ability to differentiate into cells that make up the placenta.

Answer 11

Pluripotent stem cells

Question 12

Stem cells that can differentiate into a few different types of cell.

Answer 12

Multipotent stem cells

Question 13

Stem cells that can only differentiate into one type of cell.

Answer 13

Unipotent stem cells

Question 14

Describe the process of stem cells becoming specialised:

Answer 14

• Under the right conditions, some genes are expressed and others are switched off.
• mRNA is only transcribed from specific genes.
• mRNA from these genes is translated into proteins.
• Proteins modify the cell - determine the cell structure and control cell processes.
• Changes to the cell produced by proteins = cell is specialised.

Question 15

Give an example of a cell becoming specialised:

Answer 15

• Stem cell produces new cell where the genes for haemoglobin production are expressed.
• Other genes, eg. those involved in removing the nucleus, are expressed too.
• Many other genes are not expressed.
• Specialised red blood cell forms.

Question 16

Cardiomyocytes

Answer 16

Heart muscle cells that make up the heart tissue.

Question 17

What was previously thought about cardiomyocytes?

What has new research shown?

Answer 17

Previously thought they could not divide to replicate themselves.

Research has suggest hearts have some regenerative capability.

Question 18

What is the main use of stem cells?

Answer 18

• Stem cell therapy to treat disorders.

Question 19

What diseases do stem cell therapies already exist for?

Answer 19

Diseases affecting the blood and immune system.

Question 20

What does bone marrow contain?

Answer 20

Stem cells that can become specialised to form any type of blood cell.

Question 21

What are bone marrow transplants used for?

Answer 21

To replace the faulty bone marrow in patients that produce abnormal blood cells.

Question 22

What has stem cell therapy been successfully used for?

Answer 22

To treat leukaemia (cancer of the blood or bone marrow) and lymphoma (a cancer of the lymphatic system).

Question 23

What is SCID?

Answer 23

Severe combined immunodeficiency.

A genetic disorder that affects the immune system.

Question 24

How does SCID affect an individual?

Answer 24

• Poorly functioning immune system as white blood cells are defective.
• So they can’t defend the body against infections by identifying and destroying microorganism.
• Leaves them extremely susceptible to infections.

Question 25

What is the treatment for SCID?

Answer 25

* Bone marrow transplant replaces faulty bone marrow with donor bone marrow that contains stem cells without faulty genes. * These differentiate to produce functional white blood cells - can identify and destory invading pathogens = immune system functions properly.

Question 26

What uses of stem cells are scientists researching?

Answer 26

* Spinal cord injuries - replace damaged nerve tissues * Heart disease and damage to heart . * Bladder conditions - grow new bladders which can replace diseased ones. * Respiratory diseases - donated windpipes can be stripped to collagen structures and covered with tissues generated by stem cells. * Organ transplants - organs can be grown from stem cells to provide new organs for people on donor waiting lists.

Question 27

What are the two main benefits of stem cells?

Answer 27

* Could save many lives - eg. could be used to grow new organs for people awaiting transplants. * Could improve quality of life - eg. replace damaged cells in blind patients.

Question 28

What are the 3 main potential sources of human stem cells?

Answer 28

* Adult stem cells * Embryonic stem cells * Induced pluripotent stem cells (iPS cells)

Question 29

Where are embryonic stem cells obtained from? *How?*

Answer 29

Obtained from body tissues of an adult, eg bone marrow. Obtained through a simple operation - little risk but lots of discomfort.

Question 30

What is the main limitation of adult stem cells?

Answer 30

Not as flexible as embryonic - they're multipotent.

Question 31

Where are embryonic stem cells obtained and how?

Answer 31

From embryos at early stage of development. * In vitro fertilisation - fertilises egg cells outside the womb. * At approx. 4-5 days old stem cells are removed. * Embryo destroyed. *

Question 32

What type of stem cells are embryonic stem cells?

Answer 32

Pluripotent

Question 33

What type of stem cells are adult stem cells?

Answer 33

Multipotent

Question 34

What are iPS cells?

Answer 34

Induced pluripotent stem cells. Created by scientists in the lab by 'reprogramming' specialised adult body cells so that they become pluripotent.

Question 35

How are adult body cells turned into iPS cells?

Answer 35

* Made to express a series of transcription factors that are associated with pluripotent stem cells. * Caused by transcription factors.

Question 36

How can transcription factos be introduced to the adult stem cells to help them become iPS cells?

Answer 36

* Infection with a specially-modified virus. * Virus contains genes coding for transcription factors within its DNA. * Upon infection, these genes are passed into adult cell's DNA. * Adult stem cell can now produce transcription factors.

Question 37

Why is the use of iPS cells currently limited?

Answer 37

More research is needed to test the similarity to true pluripotent embryonic stem cells.

Question 38

What are some ethical issues surrounding stem cell usage?

Answer 38

* Destruction of an embryo - could become a fetus if placed in womb.

Question 39

What would be a solution to the ethical issues surrounding the use of embryonic stem cells?

Answer 39

iPS cells - can be as flexible as embryonic cells but don't result in the destruction of an embryo.

Question 40

How could iPS cells become even more useful?

Answer 40

If they are made from a patient's own cells - would be genetically identical to patient's cells and so wouldn't reject.