B5 - Animal Development

ANIMAL DEVELOPMENT

To start with,  the cells in the embryo are all the same = embryonic stem cells

Embryonic stems cells are UNDIFFERENTIATED - (they're able to divide to produce any type of specialised cells)

In humans all the cells in the embryo are undifferentiated up to the eight cell stage

The process of stem cells becoming specialised = DIFFERENTIATION

After the 8 cell stage , most of the stem cells in a human embryo start to differentiate . The embryo then begins to develop tissues. Tissues= (groups of specialised cells) and organs (groups of tissues)

Adult humans only have stem cellls in certain places like the bone marrow. Adult stem cells can become specialsied but they aren't as versatile as embryonic stem cells - they can only differentiate into certain types of cell.

All body cells contain the same genes, but in specialised cells most of the genes aren't active - they only produce the specific proteins they need. Stem cells can switch on any gene during their development 

Already used to cure diseases.

For example, people with some blood diseases (eg. sickle-cell anaemia) can be treated by bone marrow trasplants . 

Bone marrow contains stem cells that can turn into new blood cells to replace faulty old one

Embryonic stem cells can be extracted from very early human embryos

These could then be made to differentiate into specific cells to replace faulty cells in sick people (heart muscle celss for people with heart diseases)

To get one specific type of cell, scientists try to control differentiation of the stem cells by altering the conditions to activate certain genes. It's a bit tricky and more research is needed.

But some people think it's unethical to use embryonic stem cells because the embryos used to provide the stem cells are destroyed and they could have become a person.

Embryonic stem cell research is regulated by the government 

1. Take an egg cell and remove its genetic material

2. A nucleus from a body cell of the adult you're cloning is then inserted into the 'empty' egg cell

3. Under the right conditions, inactive genes in the nucleus of the body cell can be reactivated (switched on) so that an embryo forms

4. Embryonic stem cells can then be extracted from the embryo - these stem cells could then be controlled to form any type of specialised cell.