Whitehead Institute Glossary of Stem Cell Terms

Adult stem cells: A stem cell found in specialized tissue that can renew itself and (with certain limitations) divide to yield all the specialized cell types of the tissue from which it originated.

Cancer stem cells: Cancer cells that are composed of self-renewing, less differentiated stem cells.

Cellular program: How a cell reads its genetic make-up, shutting down certain segments of some genes and activating segments of others.

Chromosome: A thread-like gene-carrying structure found in the nucleus of a cell. Different organisms have different numbers of chromosomes. Humans have 23 pairs of chromosomes, 46 in all: 44 autosomes and 2 sex chromosomes. Each parent contributes one chromosome to each pair, so children get one half of their chromosomes from their mother and one half from their father.

Cytoplasm: The contents of a cell other than the nucleus; cytoplasm consists of a fluid containing numerous structures, known as organelles, that carry out essential cell functions.

Differentiation: The specialization of cells to perform particular tasks.

DNA: Abbreviation for deoxyribonucleic acid which makes up genes.

Embryonic stem (ES) cells: Primitive (undifferentiated) cells from the embryo that have the potential to become a wide variety of specialized cell types.

Embryo: In humans, the developing organism from the time of fertilization until the end of the eighth week of gestation, when it becomes known as a fetus.

Epigenetic: The changes within cells that lead to the development of the various specialized cell types throughout the body.

Gametes: Reproductive cells that unite during sexual reproduction to form a fertilized egg (zygote). Male gametes are sperm and female gametes are eggs.

Gene: A heredity unit comprised of a segment of DNA located in a specific site on a chromosome. A gene directs the formation of a protein.

Genome: An organism’s genetic material, in most cases composed of one or more long DNA molecules. The human genome consists of 46 chromosomes.

Hematopoietic stem cell: A stem cell from which all cells of the immune system and all red and white blood cells develop.

In vitro: In a test tube or Petri dish, as opposed to in an organism (in vivo).

Multipotent: Describing a cell which can give rise to many types of cells, but not all.

Nucleus: Central cell structure that houses the chromosomes—the genetic material.

Oligopotent: Describing a cell which is only capable of generating a few cell types within a particular tissue.

Organism: An individual form of life.

Pluripotent: A cell capable of giving rise to most tissues of an organism. Embryonic stem cells are pluripotent.

Regenerative medicine: Seeks to understand how and why stem cells, whether derived from human embryos or adult tissues, are able to develop into specialized tissues, and seeks to harness this potential for tissue-replacement therapies that will restore lost function in damaged organs.