Blastocyst The preimplantation embryo of mammals
consisting of a sphere of cells with an outer cell layer that
forms the placenta (trophectoderm) and a cluster of cells on the
interior called the inner cell mass that forms the embryo and
from which embryonic stem cells may be derived
Cell nuclear replacement (CNR) The process whereby
a nucleus (which contains almost all the DNA of the human/animal
in question) is placed in an egg in which the nucleus has been
removed. This process of cell nuclear replacement led to the birth
of the sheep Dolly and since then CNR has been successfully used
to generate clones of other animal species
Chimera In experimental embryology, the term
'chimera' refers to a single individual made by combining two
or more embryos, or mixing pluripotent cells from more than one
embryo, either of the same or of another species
Cytoplasmic hybrid embryos The term used in this
report to describe embryos created through somatic cell nuclear
transfer into enucleated ova, and specifically in relation to
recent applications from researchers at King's College London
and Newcastle University to create such entities through transfer
of human genetic material into enucleated animal ova.
Differentiate The term used to describe the progressive
cellular changes required to become a more specialized cell type
and the process cells undergo as they mature into normal cells.
Differentiated cells have distinctive characteristics and perform
Deoxyribonucleic acid (DNA) The material inside
the nucleus of cells that carries genetic information
Embryo An animal in the early stage of development
before birth. In humans, the embryo stage is the first three months
Enucleated animal ovum (EAO) An egg from which
the nucleus has been previously removed
Eukaryotic cell A cell which contains a nucleus
and other membrane-bound organelles (e.g. mitochondria)
Hybrid 1. Offspring produced from mating plants
or animals from different species or varieties. 2. cell produced
by fusing cells of two different origins, usually of two different
species. Usually referred to as 'somatic cell hybrid'. 3. In the
context of this inquiry, the term 'hybrid' is used to describe
the creation of an embryo after implanting human DNA into an enucleated
Gametes Male or female reproductive cells i.e.
the sperm or the egg
In vitro Literally,
"in glass." The term used to refer to experiments performed
in a test tube or other laboratory apparatus.
In vitro fertilisation
(IVF) A method of assisted reproduction involving combining
an egg with sperm in a laboratory dish. If the egg fertilizes
and begins cell division, the resulting embryo can be transferred
into the woman's uterus where it may implant in the uterine lining
In vivo Refers to
biological processes that take place within a living organism
or cell and is the term used to describe experiments carried out
in living organisms
Mitochondria Structures (found within the cell)
responsible for providing the cell with energy. Mitochondria have
their own DNA, distinct from the nuclear DNA in the cell.
Morula The ball of cells which forms at about
4 days after insemination of the egg.
Mutant cell A cell which differs from the wild
type because it carries one or more genetic changes in its DNA.
Nucleus The part of the cell that contains the
majority of the genetic material (DNA).
Ova (plural), Ovum (singular),
Oocyte (additional term) A female
sex cell, or egg
Pluripotency The ability to develop into multiple
Preimplantation Genetic Diagnosis (PGD) A technique
in which embryos are tested for specific genetic disorders before
being implanted into the uterus.
Somatic Any type of cell other than that used
in reproduction (i.e. egg or sperm)
Somatic cell nuclear transplantation (SNCT) The
process by which a cell nucleus is removed and placed into an
enucleated animal ovum
Stem Cell Cells that can give rise to other types
of cells; they are produced both during embryonic development
and in the adult body.
Therapeutic cloning The use of somatic cell nuclear
transfer to produce embryonic stem cells suitable for differentiation
into tissues that are a perfect match to treat disease in the
person who provided the cell nucleus used.
Wild-type cell The normal, non-mutant form of