Glossaire
A - D | E - H | I - O | P - S | T - Z
A
Adult stem cells
Undifferentiated cells found in various tissue within the human body, which can renew itself and give rise to specialized cell types and tissue from which the cells came. Scientists are unclear as to whether or not these cells can give rise to cell types other cell types in the body.
B
Blastocyst
A preimplantation embryo of 30-150 cells. The blastocyst consists of a sphere made up of an outer layer of cells (the trophectoderm), a fluid-filled cavity (the blastocoel), and a cluster of cells on the interior (the inner cell mass).
C
Cell division
method by which a single cell divides to create two cells
Cell line
cells that can be grown and maintained in a culture which appear to regenerate and have an indefinite life span
Chimera
An organism composed of cells derived from at least two genetically different zygotes, from the same or different species. Chimerism can be produced experimentally at different stages of development, from embryo through to adult.
Chromosomes
The structures within the nucleus that consist mostly of DNA and determine the genetic makeup of the organisms. Chromosomes contain genes, working subunits of DNA that carry the genetic code for specific proteins, interspersed with large amounts of DNA of unknown function. A normal human body cell contains 46 chromosomes, half of which are contributed by the father and half by the mother.
Clone
generation of a cell which is genetically identical to the original cell.
Cloning
Generation of an embryo by somatic cell nuclear transfer
Cloning, reproductive
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.
Cloning, therapeutic
Sometimes used to refer to cloning of an embryo for the purpose of deriving pluripotent stem cells for therapeutic application.
D
Differentiation
The process by which cells acquire new characteristics and form more specialized cell types.
Directed differentiation
coaxing stem cells to differentiate into different cell types
DNA
Deoxyribose nucleic acid; the genetic material of the chromosomes.
E
Embryo
An organism in the early stages of development; in humans, up to about 6 weeks of development.
Embryo provider
A couple (occasionally an individual) having custody of an embryo and the authority to make decisions regarding its disposition; not always the biological parent(s) of the embryo.
Embryonic germ (EG) cells
Pluripotent stem cells derived from cells in the fetal gonad that would normally develop into mature gametes.
Embryonic stem (ES) cells
Pluripotent stem cells derived from the inner cell mass of a blastocyst stage embryo.
F
Fetus
An organism from the end of the embryonic period ( 6 weeks of development in the human), up to birth.
G
Gamete
The sex cell (sperm or egg). The functional, mature, male gamete is called a sperm while the female gamete is called the ovum, or egg.
Gamete provider
A person who is a biological parent of the embryo, but does not necessarily have custody of the embryo or any authority to make decisions regarding its disposition.
Gonad
An organ that produces sex cells (a testis or an ovary)
H
Hematopoietic
Related to the formation of blood cells, a process that occurs mainly in the bone marrow.
Hematopoietic stem cell
precursors of mature blood cells that give rise to all red and white blood cells and platelets
Human embryonic stem cell (hESC)
a type of pluripotent, self-renewing stem cell which is derived from the inner cell mass of a developing blastocyst.
I
In vitro fertilization (IVF)
Fertilization of an egg by a sperm outside a woman's body.
Inner cell mass
a small cluster of cells within the blastocyst
M
Mesenchymal stem cells
Mitosis
cell division
Morula
The stage of the embryo just prior to the blastocyst which consists of a ball of unspecialized cells.
Multipotent
the ability of a cell type to change into more than one type of cell within the body
N
Neural
Related to the cells of the nervous system.
Nucleus
The portion of the cell enclosing the genetic material of the chromosomes.
O
Oocyte
An immature ovum (egg).
Ovum
See "gamete".
P
Plasticity
the ability of one cell type from one tissue type to generate another cell type of another tissue
Pluripotent stem cell
A stem cell with the capacity to differentiate into cells of all germ layers (endoderm, ectoderm, and mesoderm). These are usually derived from early embryos or embryonic germ cells.
Progenitor cell
a cell type that can differentiate, but not regenerate, but cannot renew itself
R
Regenerative medicine
using stem cells to replace damaged cells and tissue
Reproductive cloning
creating a fetus through somatic cell nuclear transfer from a cell which is genetically identical to the cell donor
S
Somatic cell nuclear transfer
nuclear transfer, nuclear replacement: see 'cloning'; The transfer of a nucleus from a somatic cell into an unfertilized egg (oocyte) which has had its nucleus removed (i.e. has been 'enucleated').
Somatic cells
The cells of an organism, other than those cells whose descendants may include gametes.
Sperm
See "gamete".
Stem cell
A cell that has the ability to divide for indefinite periods in culture and to give rise to specialized cells.
Stromal cell
a cell from the body other than gamets
T
Therapeutic cloning
Somatic cell nuclear transfer in order to produce embryonic stem cells which are an exact match to the donor. The donor's somatic cells are implanted into an enucleated egg. The embryonic stem cells are then harvested, and may be used to coaxed to differentiate into a particular cell type, and used to repair damaged tissue.
Totipotent cells
Cells of the very early embryo that have the capacity to differentiate into the placenta, the embryo, and all postembryonic tissues and organs. No stem cell line to date has been shown to have these properties.
Transdifferentiation
the process by which a cell from one tissue may differentiate into a cell type of another tissue.
U
Umbilical cord blood stem cells
small amounts of hematopoietic stem cells which may be harvested from the umbilical cord at birth. These cells are similar to those residing within the bone marrow, and may be used for the treatment of leukemia, and other diseases of the blood.
Z
Zygote
A fertilized egg formed as a result of the union of the male (sperm) and female (egg) sex cells.