20.2: Stem cells and totipotency

Question 1

What is Cell Differentiation

Answer 1

The process by which a cell develops into a specialised structure

Question 2

What is Totipotency

Answer 2

The ability to mature into any type of body cell which can become specialised

Question 3

What occurs during Cell Specialisation

Answer 3

During cell specialisation, only some genes are expressed.

Only part of the DNA of a cell is translated into proteins. The cell therefore only makes proteins to carry out its specialised function

Question 4

How are genes turned off

Answer 4

1. Transcription is prevented, stopping the production of mRNA
2. Translation is prevented, stopping the formation of a polypeptide

Question 5

What are stem cells

Answer 5

Stem cells are undifferentiated cells capable of developing into any type of body cell

Question 6

Features of Stem cells

Answer 6

1. Undifferentiated
2. Dividing
3. Self-Renewable

Question 7

Origins of Stem cells

Answer 7

Embryonic stem cells - from embryos and can differentiate into any type of cell

Umbilical cord blood stem cells - derived from the umbilical cellls and are specific to a particular tissue or organ

Placental stem cells - found in the placenta and develop into specific types of cells

Adult stem cells - found in the body tissues of the fetus to the adult. Specific to a particular tissue/organ within which they produce the cells to maintain and repair tissues

Question 8

Types of Stem cells

Answer 8

Totipotent - Found in the embryo and can differentiate into any type of cell (zygote)

Pluripotent - found in embroys and can differentiate into almost any type of cell (embryonic)

Multipotent - found in adults and can differentiate into a limited number of specialised cells. (adult stem cells, cord blood stem cells)

Unipotent - Can only differentiate into a single type of stem cell. Derived from multipotent

Question 9

What are Induced Pluripotent Stem Cells (iPS)

Answer 9

Type of Pluripotent stem cell produced from unipotent stem cells.

The unipotent cell may be almost any body cell, these body cells are then genetically modified to make them acquire the characteristics of an embryonic stem cell. This is done by inducing genes and transcriptional factors

iPS are very similar to embryonic stem cells, but not identical. They have the capability to replace embryonic stem cells in research

Question 10

Pluripotent stem cells in treating human disorders

Answer 10

B cells in the pancreas - type 1 diabeties

Heart muscle cells - heart attack