Topic 17 Stem Cells

Question 1

what are stem cells?

Answer 1

• rapidly dividing cells that can develop into other specialised cells through mitosis while remaining undifferentiated (unspecialised) themselves (self renewal)

Question 2

how do plants and animals compare in terms of number and distribution of stem cells?

Answer 2

• plants have more stem cells, they are located everywhere, allows growth their whole life
• makes it easier for plants to be cloned as more stem cells will be present in smaller piece of tissue
• animals have fewer, in early embryo and some adult cells, where new cells are needed (eg bone marrow)

Question 3

how does a zygote develop?

Answer 3

• zygote divides into small ball of cells - early embryo
• these are embryonic stem cells and can divide and produce any cell type
• gradually differentiate and become specialised for particular function.
• at this later point, cells only expressing some genes (eg nerve cells only express nerve genes)

Question 4

why are stem cells important?

Answer 4

• stem cells are unspecialised cells, but can divide by mitosis to produce daughter cells that can differentiate into specialised cells
• specialised cells are important becuase they carry out particular functions - esp, important for tissues, which are groups of similar specialised cells, carrying out a particular function

Question 5

what is the difference between embryonic and adult stem cells?

Answer 5

• embryonic can differentiate into all different types of specialised cells
• adult has limited ability to differentiate - role is to replace cells lost through damage/for growth -> bone marrow makes blood cells

Question 5

what is the difference between embryonic and adult stem cells?

Answer 5

• embryonic can differentiate into all different types of specialised cells
• adult has limited ability to differentiate - role is to replace cells lost through damage/for growth -> bone marrow makes blood cells

Question 5

how are stem cells used in medicine?

Answer 5

• human embryos can be grown in a lab and embryonic stem cells extracted - to repair damaged organs etc
• adult stem cells can be cultured in lab and made to differentiate into specialised cells (mostly blood cells)

Question 6

evaluate the use of stem cells in medicine

Answer 6

benefits
- potential to treat wide variety of diseases eg diabetes, paralysis, leukemia
- organs developed from a patients own stem cells -> reduces risk of rejection

risks
- stem cells cultured in lab could become infected with virus which could be transmitted to patient
- risk of cultured stem ccells accumulating mutations that can lead them to develop into cancer cells

social issues
- embryonic stem cells can be collected before birth, or after birht, and stored by a clinic, but this is expensive
- lack of peer reviewed clinical evidence of success of stem cell treatments
- stem cells sourced from unused human embryos in ivf treatment - does it have rights?
- undermines respect for human life