20.2 Stem cells and totipotency

Question 1

What is cell differentiation

Answer 1

The process by which each cell develops into a specialised structure

Question 2

What are totipotent cells

Answer 2

Cells that can mature into any body cell

Question 3

How are genes prevented from expressing themseles

Answer 3

1. Preventing transcription and so preventing the production of mRNA
2. Preventing translation

Question 4

What are stem cells

Answer 4

Undifferentiated dividing cells that occur in adult animal tissues and need to be constantly replaced. They therefore divide to form an identical copy of themselves in a process called self-renewal

Question 5

What are the 4 sources of stem cells

Answer 5

1. Embryonic stem cells - from embryos and differentiate into any type of cell
2. Umbilical cord blood stem cells - from cord blood and similar to adult stem cells
3. Placental stem cells - found in the placenta and develop into specific cell types
4. Adult stem cells - found in the body tissues of the fetus through to the adult. Specific to a particular organ or tissue.

Question 6

What are the 4 types of stem cells

Answer 6

1. Totipotent stem cells - found in the early embryo and can differentiate into any type of cell. Zygotes are totipotent
2. Pluripotent - found in embryos and can differentiate into almost any type of cell. Embryonic and fetal stem cells
3. Multipotent - Found in adults and can differentiate into a limited number of specialised cells
4. Unipotent - Can only differentiate into a single type of cell. Derived from multipotent stem cells and are made in adult tissue.

Question 7

What are induced pluripotent stem cells

Answer 7

iPS cells are a type of pluripotent cell that is produced from unipotent stem cells. - which are derived from multipotent cells

The unipotent cell may be almost any body cell. These are then genetically altered to make them acquire the characteristics of embryonic stem cells - which are pluripotent.

Question 8

How do we make a unipotent cell acquire new characters

Answer 8

Inducing genes and transcriptional factors within the cell to express themselves. We turn on genes that were turned off.

Question 9

What can iPS cells do

Answer 9

Divide themselves infinitely, self-renewal.

Question 10

Why are iPS cells ethically sound

Answer 10

Because they’re similar to embryonic stem cells yet overcome the ethical issures of using embryos

Question 11

What can pluripotent stem cells be used in regards to medicine

Answer 11

1. Regrow tissues that have been burnt
2. Regrow tissues that have been destroyed as a result of Parkinsons
3. Blood cells damaged by leukaemia
4. Beta cells of the pancreas as a result of type 1 diabetes.