Stem Cell Terms

Glossary of Stem Cell Terms


Adult Stem Cell: A stem cell from organs and tissues, usually after birth (including umbilical cord and placenta), that can renew itself and transform into other specialized cell types.  

Assisted reproductive technology: Fertility treatments that involve a laboratory handling eggs or embryos, such as in vitro fertilization.

Blastocyst: Early stage of embryo, approximately 5-7 days after conception (50-250 cells.) 

Cloning: Creation of an animal or person that derives its genes from a single other individual; “asexual reproduction”.  Creating a copy that is virtually identical to the original (can be done with molecules, cells, and whole organisms.) 

Chromosomes: Contain genes, working stretches of DNA that carry the genetic code for specific proteins.  Normal human cells contain 46 chromosomes; mature normal human gametes have 23 chromosomes. 

Differentiation: The process by which early unspecified cells become specialized cells such as heart, liver, muscle, or brain tissue. 

DNA: DeoxyriboNucleic Acid.  The genetic material that contains the instructions for making an entire organism. 

Embryo: The earliest stage of human development, from the single cell zygote up to about 8 weeks. 

Embryonic germ cell: A cell in the embryo/fetus that normally develops into mature gametes. 

Embryonic stem cell: A cell from the inner mass of cells of a blastocyst, with the potential to become most or all of the body tissues. 

Fetus: The human being from 8 weeks after conception to birth.

Gamete: A mature germ cell (egg or sperm), which unites with another in sexual reproduction. 

Gene: A unit of heredity that is a segment of DNA located on a specific site on a chromosome.

In vitro: Done outside of the body.

In vivo: Done within the living body. 

Multipotent: Capable of giving rise to several specialized cells or tissues of an organism. 

Nucleus: The core of a cell that contains the chromosomes (genetic material.) 

Pluripotent: Capable of giving rise to most tissues of the adult body. 

“Reproductive Cloning” (Live-Birth Cloning): All cloning is reproductive in that it creates – reproduces – a new developing human intended to be virtually identical to the cloned subject.  The term “reproductive cloning” has been used to signify the implantation into a womb of a cloned embryo, in hopes of a live birth. 

Somatic cell: Cell of the body other than a gamete (other than an egg or sperm.) 

Somatic cell nuclear transfer: Cloning.  The transfer of a cell nucleus from a body cell into an egg from which the chromosomes have been removed or inactivated; the method used for cloning of an organism.  Once the transferred genome is within the egg cell and a one-cell embryo is created, the process of cloning is complete and further development of the clone can occur. 

Stem cells: Unspecialized cells with the capacity to self-renew and to transform into other mature cell types 

“Therapeutic Cloning” (Experimental Cloning): Creating a cloned embryo for the purpose of destroying it to harvest embryonic stem cells or tissues, or for other experimental studies. 

Tissue culture or cell culture: Growth of cells or tissues in a laboratory dish for experimental research. 

Totipotent: Capable of giving rise to all tissues and organs, including placenta. 

Zygote: A one-cell embryo.  Even at this stage the embryo is a human being (species Homo sapiens).