Cell Types:
Adult Stem Cells: Undifferentiated cells throughout the body that divide to
replenish dying cells and regenerate damaged tissues (i.e. hematopeietic
cells of the bone marrow).
Cord Blood Stem Cells: Stem cells derived from the blood of the placenta and
umbilical cord after birth.
Embryonic Stem Cell: Cells cultured from the undifferentiated inner cell
mass of an early stage embryo (blastocyst of a human embryo-between 50 and
150 cells big)-this destroys (kills) the human embryo.
Induced Pluropotent Stem Cells (IPCS): Inducing adult somatic cells to
behave as Embryonic Stem Cells.
Somatic Cell: Fully differentiated non-stem cells that do not have
self-renewal tendencies.
Stem Cell-General: Primal undifferentiated cells that retain the ability to divide
and differentiate into other cell types.
Chimera: An animal with features of at least 2 different species, such as a
horse with a goats head! Mice with human brain cells implanted; it has been
attempted!
Cloning Definitions:
Cloning-General: Creating a new organism or group of cells with the same genetic
information as an existing cell. It is an asexual method of reproduction
because fertilization with another gamete does not take place. A nucleus is
removed from the receiving egg (oocyte) and the nucleus of a donor somatic
cell is injected into it. If the donor nucleus is from the same maternal
line the mitochondrial genome is also transferred; if not, it is not also
transferred (cross-species mitochondrial genome transfer can result in
incompatibilities or inviability-death).
Therapuetic Cloning: Process involving somatic cell nuclear transfer (SCNT)
or altered nuclear transfer (ANT) which uses an egg (oocyte) of which the
nucleus has been removed and replaces it with the nucleus from another donor
cell. In humans this creates an embryo from which stem cells can be
harvested-the embryo killed in the process. Scientists are trying to argue
that by using the technique of altered nuclear transfer (ANT-see below)
there is not really an embryo developed (the nucleus or the genetic material
is altered to not allow the cells (an embryo!) to develop past a certain
point).
Reproductive Cloning: Implanting the created human clone (made from taking
an egg (oocyte) from which the nucleus has been removed and replacing it
with the nucleus from another donor cell-SCNT) into a uterus and taking it
to term or birth.
Nuclear Transfer: Transferring the nucleus from one cell to another one; exchanging it for that cell's nucleus.
Altered Nuclear Transfer (ANT): The nucleus of a somatic cell is removed and
inserted into an egg cell in which the nucleus has been removed and
discarded. The difference in ANT from SCNT is that the nucleus or cytoplasm
of the egg is supposedly ‘altered’ to make a stem cell that lacks embryo
potential (no embryogenesis-no embryo development).
Altered Nuclear Transfer/Oocyte Assited Reprogramming (Ant-Oar): The Nucleus
of a somatic cell is removed and inserted into an egg cell in which the
nucleus has been removed and discarded. The difference in Ant and Ant-Oar is
that instead of knocking out a gene for development, genes are
"jump-started" to skip the Totipotent embryo stage and move directly to the
Pluripotent stem cell stage. Supposedly never becoming an embryo at all but
leaving embryonic stem cells to use.
Somatic Cell Nuclear Transfer (SCNT): The nucleus of a somatic cell is
removed and inserted into an egg cell in which the nucleus has been removed
and discarded.
Parthenogenesis: A process by which an embryo is created solely from a
female oocyte without genetic input from a male. An egg is either ‘kept’
from donating half of its 46 chromosomes to connect with a halved male cell
(23 chromosomes) or is stimulated to replicate its halved 23 chromosomes to
result in a full 46 chromosomes. In either case, the embryo’s full
compliment of 46 chromosomes comes solely from the female.
Plasticity: The 'flexibility' or ease of the ability to differentiate cells
Potency: Specifies the differentiation potential of the stem cell (the
potential to differentiate into different cell types):
Multipotent: Precursors of fully differentiated somatic (single type of
tissue cells); produce only cells of a closely related family of cells (i.e.
hematopoeietic stem cells that differentiate into red blood cells, white
blood cells platelets, etc.).
Pluripotent: Stem cells that are descendants of totipotent cells and can
differentiate into cells derived from the 3 germ layers (cells that give
rise to organs and tissues).
Totipotent: Stem cells that are capable of developing into the entire
organism (can differentiate into embryonic and extra-embryonic cell types).
These are ‘master’ stem cells that contain the ‘blueprint’ of development of
the whole organism.
Unipotent: Cells that can produce only one cells type, but have the property
of self-renewal which distinguishes them from non-stem cells.