T3L10/11 Stem Cells

Question 1

What is a totipotent stem cell

Answer 1

A stem cell that can differentiate into any type of human cell

Question 2

What is a pluripotent stem cell

Answer 2

Stem cells that can differentiate into every type of human body cell excluding extra-embryonic cells such as placental and umbilical cells

Question 3

What are multipotent stem cells + give examples

Answer 3

Stem cells from adult tissues that can only specialise into certain types of cells.

Example: bone marrow stem cells

Question 4

Describe potency of stem cells in an early embryo

Answer 4

After undergoing three divisions all embryonic cells are totipotent

Question 5

Describe the potency of stem cells in a blastocyst

Answer 5

Outer cell layer will from placenta
Inner mass of cells will form the embryo - these cells are pluripotent

Question 6

What are mesenchymal stem cells

Answer 6

Multipotent adult stem cells that are found in multiple tissues e.g fat tissue

Question 7

Why does it take us longer to recover from injury as we get older

Answer 7

Number of stem cells we have decreases so it takes longer to replace the damaged muscle/bone/cartilage

Question 8

Explain how stem cells become specialised

Answer 8

1 Stem cells contain the full genome for an organism
2 Stem cells receive a stimulus that activates certain genes
3 mRNA is transcribed from the active genes
4 mRNA is translated at the ribosomes
5 the proteins produced modify the cell, determining its structure
6 these changes cause the cell to become specialised

Question 9

What is potency in plants like

Answer 9

All cells remain totipotent throughout their lifetime

Plants can de-differentiate and then re-differentiate into a completely different plant

Question 10

How can plant stem cells be cloned

Answer 10

Small piece of plant placed on agar gel with nutrients in
Cells then divide to form a mass of undifferentiated cells
These cells can be made to differentiate and form embryos
These embryos can be grown into plants that are genetically identical

Question 11

What important technique is involved in growing plants cultures

Answer 11

Aseptic technique

Question 12

What are the two types of stem cells that can be used in medicine and what are the differences between them

Answer 12

Embryonic stem cells and Bone marrow stem cells

Embryonic stem cells have the ability to differentiate into any type of cell whereas Bone marrow stem cells are multipotent and can differentiate into different types of cell

Question 13

Where do stem cells come from for medical uses

Answer 13

Embryonic stem cells come from ‘spare’ embryos from IVF clinics

Bone marrow stem cells are collected from bone marrow from healthy people and donated

Question 14

At what stage are embryonic stem cells from

Answer 14

Blastocyst - main cell mass

Question 15

What biological issues can arise from the use of donor stem cells and how can this be combatted

Answer 15

Rejection
so
Immunosuppressant drugs

Question 16

What is one way to overcome the risk of rejection of stem cells

Answer 16

Use bone marrow stem cells from the patient themselves

Question 17

Name advantages of using embryonic stem cells

Answer 17

They can develop into any type of specialised cell

Question 18

Name the disadvantages of using embryonic stem cells

Answer 18

• Embryonic stem cells can only be used up to 14 days after fertilisation
• Some have ethical issues based on religious objections - is life destroyed when the embryo is discarded?
• Risk of rejection

Question 19

Name the advantages of using bone marrow stem cells

Answer 19

• Cells are obtained from body (no ethical issues as patient can consent)
• Simple low-risk operation
  -Lower risk of rejection if own patient’s stem cells are used

Question 20

Name the disadvantages of using bone marrow stem cells

Answer 20

There are a limited number of different type of specialised cells that embryonic stem cells can becom e

Question 21

Describe how therapeutic cloning works

Answer 21

Patient needs stem cell treatment

Donated Ovum is denucleated
Somatic diploid cell from patient denucleated
Nucleus from patient cell placed into ovum
Zygote like diploid cell identical to genome of patient

Cell undergoes stimulated mitosis to produce a blastocyst

Stem cells harvested from blastocyst to be used in treatment

Question 22

What does the law say about therapeutic cloning

Answer 22

Embryos must be destroyed after 14 days

Question 23

What are the benefits of therapeutic cloning

Answer 23

Animal ova can be used instead so process is not limited by human supply

No risk of rejection

No need for immunosupressants

Question 24

What does iPSC stand for

Answer 24

induced Pluripotent Stem Cells

Question 25

Describe how iPSC works

Answer 25

Use of transcription factors activates certain genes so that somatic cells dedifferentiate

Cell reverts to pluripotent state - stem cells available for treatment

Question 26

Describe benefits of iPSCs

Answer 26

No risk of rejection or ethical issues
Can differentiate into all somatic cells

Question 27

What is HFEA

Answer 27

Human fertility and embryology authority

Determine laws and regulation on use of human embryos in medicine and research

Question 28

Name examples of laws around embryology

Answer 28

Embryos may be used for research on fertility, misscarriage, gene abnormalities and contraception etc

Embryos must be discarded within 14 days

Since 2007 human-animal hybrid embyros are illegal to be used

No reproductive clonign

Question 29

What is the relationship between parliament and HFEA in terms of new laws and regulation

Answer 29

Parliament creates new laws
but
Regulatory authorities like HFEA advise based on research and peer knowledge