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
The subtelocentric and acrocentric chromosomes
are important karyological characters for the Fritillaria taxa.
In their scenario, the ancestral karyotype might have consisted of 60 mostly acrocentric chromosomes
and similar changes could have happened independently in various separate lineages.
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
Robertsonian translocations are structural chromosomal abnormalities caused by fusion of two acrocentric chromosomes
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.
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).
All observed karyotypes were characterized by a large number of small chromosomes and composed of 8 pairs of metacentric chromosomes, common to the populations of Ilheus, Belmonte and Una, plus a variable number of acrocentric chromosomes
ranging between 37 and 38 pairs (Fig.
Silver nitrate stain show up to 8 chromosomes with positive NOR located in the distal region of the long arm of acrocentric chromosomes
This characteristic has been proposed by some authors as a conserved trait for this family, suggesting that the ancestral karyotype consisted of 48 acrocentric chromosomes
(THOMPSON, 1979; MARTINS et al.