stem cells

types of stem cells

1. zygotic

2. embroyonic

3. adult (e.g. lymphoid and myeloid stem cell )

general characteristics of stem cells

1. self renewal ability

2. undifferentiated and unspecialised

3. DS of stem cells can differentiate

self renewal ability

def: cell undergoes mitosis to generate another cell that has the same potential

undifferentiated and unsecialised

stem cells do not have cell specific structures to carry out specific functions

DS has ability to differentiate

DS can differentiate int specialised cells by turning on/off expression of specific genes leading to differntial gene expression

zygotic stem cell

potency: totipotent : can differentiate self renewal into any cell type, including extra-embroyonic tissues

derived from morula

function : divide via mitosis to form blastocysts that eventually develops into the whole organism

embryonic stem cell

potency: pluripotent : can differentiate into almost any cell type except those of extra embryonic tissues derived

derived from inner masss of blastocyst

function: divide and differentiate to multiple specialised cell types to give rise to specific organs

adult stem cells

potency: multipotent : can differentiate into limited range of cell type of a specific lineage.

derived from specialised tissues

function:generate continuous supply of different cells from growth and repair

myeloid and lymphoid stem cell

adult blood stem cells in bone marrow can further divide to from myeloid and lymphoid stem cells

myeloid and lymphoid stem cells are multi potent as they can diff into various mature blood cells

myeloid stem cell: can diff into rbc, platelets, and wbc

lymphoid stem cells: can diff into 3 diff types of wbc: B lymphocytes, T lymphocytes and natural killlerrrrr cells

ethical implications of stem cells

1. destruction of embroyos: some view early embryo as a potential human being

2. medical risk: some are invasive procedures

how ips cells resolve ethical issues

1. non invasive, so fewer risks to donors

2. eliminates controversial use of embryos, as none of them were destroyed

3. eliminates risk of tissue rejection: as the patients own specialised adult cells can be reprogrammed to make the ips cells