Table 6.1AGlossary of Cytogenetic Terminology

CentromereThe constriction along the length of the chromosome that is the site of the spindle fiber attachment. The position of the centromere determines whether chromosomes are metacentric (X-shaped, e.g., chromosomes 1,3,16,19,20) or acrocentric (inverted V-shaped, e.g., chromosomes 13-15, 21, 22, Y). During mitosis the two exact copies of the DNA in each chromosome are separated by shortening of the spindle fibers attached to opposite sides of the dividing cell.
KaryotypeArrangement of chromosomes from a particular cell according to a well-established system such that the largest chromosomes are first and the smallest ones are last. See Figure 6.3. Normal female karyotype is 46,XX; normal male karyotype is 46,XY.
TranslocationA break in at least two chromosomes with exchange of material; in a reciprocal translocation, there is no obvious loss of chromosomal material. See Figure 6.4.
DeletionA segment of a chromosome is missing as the result of two breaks and loss of the intervening piece. See Figure 6.2.
InversionTwo breaks occur in the same chromosome with rotation of the intervening segment. If both the breaks are on the same side of the centromere, it is called a paracentric inversion. If they are on opposite sides it is called a pericentric inversion.
IsochromosomeA chromosome that consists of identical copies of one chromosome arm with loss of the other arm. Thus an isochromosome for the long arm of No. 17 [i(17q)] contains two copies of the long arm (separated by the centromere) with loss of the short arm of the chromosome.
CloneIn the cytogenetic sense, this is defined as two cells with the same additional or structurally rearranged chromosome or three cells with loss of the same chromosome.
DiploidNormal chromosome number and composition of chromosomes.
HyperdiploidAdditional chromosomes therefore the modal number is 47 or greater.
HypodiploidLoss of chromosomes with modal number 45 or less.
HaploidOnly one-half the normal compliment, i.e., 23 chromosomes.

From: Chapter 6, Recurring Chromosome Rearrangements in Human Cancer

Cover of Holland-Frei Cancer Medicine
Holland-Frei Cancer Medicine. 5th edition.
Bast RC Jr, Kufe DW, Pollock RE, et al., editors.
Hamilton (ON): BC Decker; 2000.
© 2000, BC Decker Inc.

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