Stem Cells

Intro

• In a multicellular organ, most cells are specialised
• However some cells remain unspecialised, these are called stem cells
• Stem cells are undifferentiatied, can keep dividing and can give rise to other cell types.

• Soon after fertilisation a zygote divides repeatedly
• These early cells are ALL stem cells, embryonic stem cells
• Theses stem cells can develop into any of the 216 cell types, they are totipotent. 
• As the embryo develops many stem cells remain, these are called pluriptent. They are able to divide into any type of cell but not the cells of the placenta.
• In adults, some cells retain this ability. They can give rise to a limited number of body tissues, multipotent stem cells.

Sources

• Main source of embryonic stem cells are from unused embryos from IVF
• Adult stem cells are found in the bone marrow
• Therapeutic cloning takes the nucleus from an ovum and replaces it with a nucleus from a body cell. The fused cells will divide and be a source of embryonic stem cells with the same genetic information as the patient. 

Uses

Stem cells could potentially be used to treat Parkinson's (a progressive loss of nerve cells), MS (destruction of nerve cells insulating layer), type 1 diabetes (cells in pancreas produce less insulin), burns (non replaceable skin cells).

Embryonic stem cells

Ads- easy to extract and grow

Disads- ethical issues, possible rejection, risk of infection, risk of cancer

Adult stem cells

Ads- Fewer ethical issues, rejection risk avoided

Disads- difficult to extract and produce, risk of infection

Fused cells

Ads- rejection risk avoided, potential of treating genetic disorders

Disads- ethical issues with source of embryonic nuclei, risk of infection and cancer.

Regulatory Authorities

• The ultimately authority figure is the parliament
• Advice is received from select committees made up of specialist advisors
• The Human Fertilisation and Embryology Authority regulated research on human embryos
• In 2011 purposes of stem cell research were extended
• The European Parliament voted to ban embryonic stem cell research but the UK disagreed. 

• Cells become specialised through differential gene expression
• Differentiated cells differ from each other as they produce different proteins
• Only certain genes are expressed at any one time
• Genes are switched on and off as and when they are needed.