Lectorial 26 - Cellular Differentiation & Approaches to Modern Medicine

meaning of differentiation

A cell that is specialised for one specific function.

Meaning of totipotent cells

a cell that can develope into any cell type

Meaning of pluripotent

A cell is able to divide into any cell type of the embryo

Meaning of multipotent

A cell is able to develop into more than one cell type, nut not all cell types

Meaning of stem cells

an undifferentiated cell that can divide to produce more stem cells or cells that go on to differentiate

Meaning of Embryonic stem cells

Derive from the inner cell mass of a mammalian embryo, which is pluripotent

Meaning of Adult stem cells

stem cells that are found in adults

What is embryonic development?

there is a progression from simple unspecialised cells to cells that are less flexible and more complex, with a specific function.

egins as a small number of totipotent cell. This means that the cells can become any cells in the body.

What occurs in the blastocyst stage of embryonic development

we can see two types of cells
- Outer cells becomes the placenta
- Inner mass cells are the embryonic stem cell.

What does it mean to say that embryonic stem cells are pluripotent?

This means they can give rise to a wide rand of cell types

Embryonic stem cells are still unspecialised, they can give rise to all cell types except the placenta

What are the exceptions to differentiations?

stem cells

germ cells

How are cells differentiated?

Control genes make proteins called transcription factors that 'switch on' other genes in the cell.

'Switching on a gene' means that it is transcribed into RNA and then translated to make proteins.

Once the control gene switches on other genes in the cell, the cell's fate has become determined. It can only become a muscle cell.

What happens to the cell as soon as the gene is turned on?

The role and fate of the gene is determined.

Summary of the steps involved in how cells differentiate

embryonic stem cells

external signal

switches on control gene which then makes transcription factors

transcription factors turn on other cell-specific genes

develops into a cell with a specific function

What makes a stem cell special?

They can divide without limit

They are undifferentiated

They can divide to give rise to both stem cells and cells which will go on to differentiate into functional tissue cells.

There are several types of stem cells, including:
- Embryonic stem cells
- Adult stem cells.

What are Induced pluripotent stem cells (iPS)

are made by "reprogramming" adult skin cells. This means that all the genes are switched off.

can be made from anyone and are genetically identical to the source skin cells. As they are also pluripotent, they can be cultured to generate any cell type

What is genomic equivalence?

The theory that all cells of an organism contain an equivalent complement of genetic information

Apart from a few immune system cells, the complete genome is present in all cells, but... during differentiation, most animal cells generally lose the ability to regenerate the whole organism because the nuclear DNA cannot reset itself to an embryonic state

What are stem cells important in modern medicine?

Gene therapy is based on the idea that it may be possible to alter the genetic code of an individual's cell. It is proposed as a way of correcting single gene disorders.

a normal allele could be inserted into the cells of the disease affect tissues.