The smallest organic unit capable of carrying out all of the functions normally attributed to life. It is a complex unit of protoplasm, usually with a nucleus, cytoplasm, and an enclosing membrane. All plants and animals are composed of these units. | cell |
A term for the kind of cell that lacks a true nucleus and divides by simple fission rather than mitosis. Bacteria and blue-green algae consist of these primitive kinds of cells. | prokaryotic cell |
A term for the kind of cell that has a true nucleus and that divides by mitosis. Complex single celled creatures such as protozoa as well as all multicelled plants and animals such as humans have these kinds of cells. | eukaryotic cell |
The selectively permeable membrane enclosing a cell. | cell membrane |
The selectively permeable membrane enclosing the nucleus of a cell. | nuclear membrane |
The term for all of the material within a cell between the nuclear and cell membranes. This material consists of water-rich viscous gel that contains numerous structures involved with cell function. | cytoplasm |
Thread-like, gene-carrying bodies in the cell nucleus. They are composed primarily of DNA and protein. They are visible only under magnification during certain stages of cell division. | chromosomes |
One of two or more strands of a chromosome. | chromatid |
A constriction in a chromosome where two or more chromatids come together. | centromere |
A standardized arrangement of pictures of an individual’s chromosomes cut out from a microphotograph of a cell and rearranged into homologous pairs according to size and other physical characteristics. This allows medical researchers to discover if an individual is a male or a female and if he/she has any gross chromosomal abnormalities. | karyotype |
Chromosomes that are paired during meiosis. Such chromosomes are alike with regard to size and also position of the centromere. They also have the same genes, but not necessarily the same alleles, at the same locus or location. | homologous chromosomes |
All chromosomes other than sex chromosomes. | autosomes |
The X and Y chromosomes which are responsible for determining whether an individual is a male or a female. | sex chromosomes |
A gene on the Y chromosome which, if present and functioning, causes the undifferentiated sex organs of an animal embryo to become testes. These then produce the hormone testosterone which, in turn, causes the development of masculine physical traits. | SRY gene |
A chromosome that is normally found only in males. | Y chromosome |
A sex chromosome that is found in both males and females. | X chromosome |