[cell division] stem cells & differentiation

[ BBC Bitesize 'Cell Biology ⇢ Cell Division' page 3-7 ] + [ AQA GCSE Biology Student Book, page 28-33 ]

Differentiation

The process of unspecialised cells becoming specialised to perform specific functions.

Stem Cells

A type of unspecialised/undifferentiated cell which have the ability to form a wide variety of (specialised) cells.

Embryonic Stem Cells

Undifferentiated cells, taken from embryos, that can differentiate into almost any cell type.

Adult Stem Cells

Undifferentiated cells, found in specific locations in adults, that can differentiate into a limited number of related cell types.

Locations of Adult Stem Cells

• bone marrow

• liver

• epidermis

• brain

• heart

• skeletal muscle

Bone marrow (stem) cells can differentiate into...

...blood cells and cells of the immune system but not other cell types.

Meristem

Region in a plant's shoots and roots, which is made up of embryonic (plant) stem cells, where cells are dividing and undergoing mitosis.

Apical Meristem

Regions of the meristem, located at the top of the root, shoot, and their branches, causing the growth of plant organs in length.

Lateral Meristem

Regions of the meristem, located on the side of the stems and roots, causing the growth of plant organs in thickness.

Zone of Cell Division/Maturation

Located right before root cap (root apical meristem), containing meristem cells that are actively dividing.

Zone of Elongation

Located between the shoot and root apical meristem, where the newly formed cells increase in length, thereby lengthening the root.

Zone of Differentiation

Located right before the shoot apical meristem, where these lengthened cells undergo differentiation.

Zygote

A fertilized egg cell, which divides and becomes a hollow ball of cells (embryo).

Possible Uses of Embryonic Stem Cells

• treating paralysis

• treating diabetes

• organ transplants

• treating macular degeneration

Advantages of Embryonic Stem Cells

• many specialised cells can be created (wide range of treatment)

• painless to extract embryonic stem cells

• will not be rejected by the immune system when introduced to body

Disadvantages of Embryonic Stem Cells

• relatively new, expensive and slow process

• difficult to control, possibly leading to tumours forming (cancer)

• ethical and religious issues; aborted or left over embryos are used

Possible Uses of Adult Stem Cells

• treating paralysis

• treating diabetes

• treating blood cell cancer such as leukaemia and lymphoma

• replacing blood cells have been destroyed by cancer treatment

• replacing blood cells have been destroyed by cancer treatment

Advantages of Adult Stem Cells

• little ethical issues -> no pregnancy is needed

• quick recovery for patients

Disadvantages of Adult Stem Cells

• fewer in number compared to embryonic stem cells

• difficult to isolate

• difficult to grow/clone/culture

• viruses in stem cells from donors can be passed to patients

Possible Uses of Plant Stem Cells

To produce new plant clones quickly and economically for:

• research

• agriculture

• horticulture (the art or practice of garden cultivation and management)

Advantages of Plant Stem Cells

• possibly help prevent extinction of plant species

• can be used to produce disease-resistant crops quickly, on a large scale

Disadvantages of Plant Stem Cells

• ethical issues -> some may believe these crops are not safe to consume.

Therapeutic Cloning

The process where an embryo is produced that is genetically identical to the patient so the cells can then be used in medical treatments.

1st Stage of Therapeutic Cloning

Nucleus from human egg cell is removed and discarded. A nucleus is removed from one of the patient’s body cells and inserted into empty egg cell.

2nd Stage of Therapeutic Cloning

The cell is now stimulated to divide. It will develop into an embryo.

3rd Stage of Therapeutic Cloning

After a few days, the stem cells are removed from the embryo and are cultured for therapeutic use.