Download Human Stem Cell Research: Opportunities for Health and

Human
Stem Cell Research:
Opportunities for Health
and Ethical Perspectives
A Discussion Paper
GLOSSARY
Blastocyst: a very early stage in mammalian development (about 1
week post-fertilization, approximately 100 cells in total). A
blastocyst consists of an inner cell mass (which develops into the
embryo and from which embryonic stem cells may be derived),
covered by a thin layer of cells known as the trophoblast (from
which the placenta develops).
Cloning: transplantation of a nucleus from a somatic cell to an
ovum (egg), which then develops into a zygote following an
appropriate stimulus.
“Therapeutic cloning”: sometimes used to refer to cloning of an
embryo for the purpose of deriving pluripotent stem cells for
therapeutic application.
“Reproductive cloning”: sometimes used to refer to cloning of an
embryo for transplantation into a uterus with the intent of
producing offspring genetically identical to the nuclear donor.
Differentiation: the process by which cells acquire new
characteristics and form more specialized cell types.
Embryo: an organism in the early stages of development; in
humans, from the 2-cell stage until approximately 6 weeks, after
which it is termed a ‘fetus’.
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Embryonic germ (EG) cell: pluripotent stem cells derived from
fetal gonads.
Embryonic stem (ES) cell: pluripotent stem cells derived from the
inner cell mass of a blastocyst stage embryo.
Gamete: the sex cell (sperm or egg). In animals (and humans) the
functional, mature, male gamete is called a sperm while the female
gamete is called the ovum, or egg.
Gonad: an organ that produces sex cells (a testis or an ovary).
Hematopoietic: related to the formation of blood cells.
Hybrid: an organism in which the chromosomes contain DNA from
two different species or subspecies.
In vitro fertilization (IVF): fertilization of an egg by a sperm in an
artificial environment.
Oocyte: an immature ovum (egg).
Pluripotent stem cells: the most primitive stem cells, with the
capacity to differentiate into the complete range of specialized cell
types.
Somatic cells: the cells of an organism, other than gametes.
Somatic cell nuclear transfer (nuclear transfer, nuclear
replacement: see ‘cloning’): inserting the nucleus of a cell from one
of the body’s organs or tissues into an unfertilized egg (oocyte)
which has had its nucleus removed (i.e. has been ‘enucleated’).
Stem cells: any cells that can renew tissue; these cells have the
property of being able to either reproduce themselves (self-renewal)
or differentiate into a variety of more specialized cell types.
Zygote: a fertilized egg formed as a result of the union of the male
(sperm) and female (egg) sex cells.
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