Karyotype in conventional staining of a female Cerradomys scotti (MN82753), collected at Fazenda Santa Cruz (locality 6), showing 2n=58, FN=68, with six pairs of biarmed and 22 pairs of acrocentric chromosomes
. X chromosome as a medium biarmed chromosome.
cariba displayed a karyotype 2n= 60, comprised of 9 pairs of metacentric (M), 15 pairs of submetacentric (SM), 1 pair of subtelocentric (ST) and 5 pairs of acrocentric chromosomes
. The chromosome arm number (NF value) equaled 110 (Figure 1a).
 This raises the prospect of determining the familial transmission of individual acrocentric chromosomes
One of the structural chromosomopathies is the Robertsonian translocation, defined as the fusion of two non-homologous acrocentric chromosomes
Jumping translocations of 1q fusing with the short-arm telomeric regions of at least one of the acrocentric chromosomes
13, 14, 15, 21, and 22 were noted in 75% (25/33) of cases.
Abdel-Basset & Fayza (2004) studied karyotype characteristics, such as chromosome size and variable morphology, including metacentric, submetacentric, and acrocentric chromosomes
, and reported chromosome length ranging from 1.90 to 0.46 [micro]m in Venus verrucosa and 1.10 to 0.50 [micro]m in Ruditapes decussatus, both from the family Veneridae.
The NORs were first described by Heitz in 1931 and by McClintock in 1934.7 These NORs are located on each of the short arms of the acrocentric chromosomes
13, 14, 15, 21 and 22.
Down syndrome (DS) is the most common autosomal abnormality and is the most genetic cause of mental retardation, appearing in about 1 of every 700 newborns.[sup], DS can be caused by three types of chromosomal abnormalities: Trisomy 21, translocation, or mosaicism.[sup] Trisomy 21 is characterized by the presence of three copies of chromosomes 21, generally resulting from nondisjunction during maternal meiosis whereas the extra chromosome 21 in mosaic DS arises from mitotic nondisjunction in a chromosomally normal zygote.[sup] For DS by translocation, the extra chromosome 21 translocated to other chromosomes or to the acrocentric chromosomes
of D and G group that is, 13, 14, 15, 21, and 22.[sup]
Because no reads aligned to the short arms of the acrocentric chromosomes
13p, 14p, 15p, 21p, 22p, and Y, these were excluded from the analysis.
Further subdivision of translocation types can be made according to the exchange of chromosomal material and are classified as: (i) reciprocal, when segments from two different chromosomes have been exchanged; or (ii) robertsonian, in five acrocentric chromosomes
(13, 14, 15, 21 and 22), where long arms fuse to form a single chromosome with a single centromere.
For example in the mammals multiple repeat copies of the rRNA are tandemly organized in a head to tail fashion on acrocentric chromosomes
and are transcribed by RNA polymerase I (Pol I).
Acanthurus coeruleus presented In = 48, composed of two submetacentric, four subtelocentric, and 42 acrocentric chromosomes