8A- Stem Cells

Question 1

Where did all specialised cells come from?

Answer 1

Stem cells

Question 2

What are stem cells?

Answer 2

Unspecialised cells that can develop into other types of cells.

Question 3

Where are stem cells found?

Answer 3

In an embryo, where they specialise to form a fetus.

Some adult tissues, where specialise cells constantly need to be replaced.

Eg, Epithelial cells.

Question 4

What are totipotent cells?

Answer 4

Stem cells that can mature into any type of body cell. (Including the placenta).

Question 5

What are pluripotent cells?

Answer 5

They can specialise into any cells apart from placenta.

Question 6

What types of stem cells are present in adult mammals?

Answer 6

Multipotent stem cells.

Unipotent stem cells.

Question 7

What are multipotent stem cells?

Answer 7

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

Eg both red and white blood cells can form from stem cells found in bone marrow.

Question 8

What are unipotent stem cells?

Answer 8

These can only differentiate to one type of cell.

Eg, epidermal skin cells.

Question 9

How do stem cells become specialised?

Answer 9

Stem cells all contain the same genes but some are switched off during translation and transcription.

mRNA is only transcribed from specific genes, which is then translated into proteins.

The proteins modify the cell and its processes, so it becomes specialised. This is difficult to reverse.

Eg red blood cells. Have no nucleus and lots of Hb due to those specific genes being expressed. It originates from the bone marrow.

Question 10

What are cardiomyocytes?

Answer 10

Heart muscle cells that make up the tissues in the heart.

It is thought they can’t replicate themselves so scientists thought we couldn’t regenerate our heart cells.

Question 11

What do some scientists now think?

Answer 11

That old or damaged cardimyocytes can be replaced my cardiomyocytes derived from a small supply of unipotent stem cells.

No one has agreed on how quickly it occurs. Some think it’s really slow and others think it’s more quickly.

Question 12

What stem cell therapies already exist?

Answer 12

Bone marrow contains stem cells that can become specialised to any type of blood cells. That can be transplanted to replace faulty bone marrow that produce abnormal blood cells.

This treatment can treat Luke Mia and lymphoma.

It can also be used to treat genetic disorders such as sickle cell.

Question 13

What other diseases can stem cells treat?

Answer 13

Spinal cord injuries- replace damage nerve tissue.

Heart disease- replace damaged heart tissue.

Bladder conditions- stem cells could be used to grow a whole bladder.

Respiratory disease- Donated windpipes can be stripped down to their collagen structure then covered by stem cell tissues and transplanted into patients.

Organ transplant- could provide organs faster than a donor list.

Question 14

What are the benefits of stem cells in medicine?

Answer 14

They could save lives by shortening waiting times for organs.

Could improve quality of life, for example, using stem cells to fix blindness.

Question 15

Where are the three main potential sources of stem cells?

Answer 15

Adult stem cells.

Embryonic stem cells.

Induced pluripotent stem cells (iPS Cells).

Question 16

How are adult stem cells used to gain human stem cells?

Answer 16

They are gained from body tissue.

It’s a simple operations with little risk but quite a lot of discomfort.

They aren’t as flexible though, they can only specialise into a limited range of cells (multipotent).

Question 17

How are embryonic stem cells used to gain human stem cells?

Answer 17

They’re obtained early on in development.

They’re created via IVF.

Stem cells are removed at 4/5 days and the embryos are destroyed.

These cells are pluripotent so can divide an unlimited number of time into all cells.

Question 18

How are induced pluripotent stem cells (iPS Cells) used to gain human stem cells?

Answer 18

IPS Cells are created in a lab.

Specialised adult cells are reprogrammed to be pluripotent.

The adult cells express a transcription factors that are associated with pluripotent cells, leading to the expression of pluripotent genes.

The transcription factors are added via a specially modified virus. When the virus infects the cell the genes are passed into the adult cell’s DNA.

Question 19

What are the ethical issues surrounding embryonic stem cell use?

Answer 19

Embryos have the potential to become a fetus.

Some people believe once fertilised the embryo has the right to life.

Some people allow stem cells from embryos that aren’t fertilised, they are artificially activated.

iPS Cells could avoid ethical issues and could be made from a patient’s own cells. It’d be genetically identical and could create organs that wouldn’t reject.