mosaic

mosaic /mo·sa·ic/ (mo-za´ik)

1. a pattern made of numerous small pieces fitted together.

2. in genetics, an individual or cell cultures having two or more cell lines that are karyotypically or genotypically distinct but are derived from a single zygote.

3. in embryology, the condition in the fertilized eggs of some species whereby the cells of early stages have developed cytoplasm which determines the parts that are to develop.

4. in plant pathology, a viral disease characterized by mottling of the foliage.

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mo·sa·ic (m-zk)

adj.

Patterned in small squares; tesselated.

n.

An organism exhibiting mosaicism.

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Mosaic

A term referring to a genetic situation, in which an individual's cells do not have the exact same composition of chromosomes. In Down syndrome, this may mean that some of the individual's cells have a normal 46 chromosomes, while other cells have an abnormal 47 chromosomes.

Mentioned in: Down Syndrome, Turner Syndrome

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mosaic

[mōzā′ik]

Etymology: L, Musa, goddess of the arts

1 an individual or organism that developed from a single zygote but that has two or more kinds of genetically different cell populations. Mosaicism may result from a mutation, crossing over, or, more commonly in humans, nondisjunction of chromosomes during early embryogenesis, which causes a variation in the number of chromosomes in the cells. The type of chromosomal aberration and the fraction of cells that are affected depend on the cleavage stage at which the causative event occurred. Because monosomic cells are nonviable, except in X monosomic conditions, most mosaic conditions caused by nondisjunction in humans represent a mixture of normal and trisomic cells, regardless of whether an autosome or the sex chromosomes are involved. The degree of clinical involvement depends on the type of tissue containing the abnormality and may vary from near normal to full manifestation of a syndrome, such as Down syndrome or Turner's syndrome. Compare chimera. See also monosomy, sex chromosome mosaic, trisomy.

2 a fertilized ovum that undergoes determinate cleavage. See also mosaic development. mosaicism, n.

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mosaic

a pattern made of numerous small pieces fitted together; in genetics, the occurrence in an animal of two or more cell populations, each having a different chromosome complement, e.g. XY/XXY mosaic.

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mosaic animals

all the genotypes arise from a single zygotic genotype because of chromosomal loss or mitotic nondisjunction.

ecological mosaic

a pattern of interspersed ecosystems of similar size and on a recurring basis.

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mosaic

adjective A patchwork of one sharply-defined 'jig-saw'-shaped pattern imposed upon another of different color, tissue pattern or radiologic density noun Genetics An individual with 2 or more genotypically or karyotypically distinct cell lines, arising from a single zygote by somatic mutation, crossing-over, or nondisjunction during mitotic division. See Chimera, Freemartin Ob/Gyn A vascular change of interconnecting vessels resulting in a cobblestone or honeycomb surface appearance by colposcopy, the mosaic pattern is often associated with CIN and mandates biopsy.