Whole-Arm Chromosome Rearrangements and Telomeric Signal Displays: Current Cytogenetic Updates on Two Target...

Area of Science:

• Cytogenetics
• Mammalian Karyotype Evolution
• Molecular Cytogenetics

Background:

• Investigates the role of whole-arm chromosomal rearrangements in mammalian karyotype evolution.
• Compares the presence of telomeric signals (tDNA-FISH) in taxa with different chromosomal rearrangements.
• Analyzes Robertsonian-like and tandem rearrangements using comparative cytogenetics of mammals.

Purpose of the Study:

• To compare the distribution of telomeric signals in mammalian karyotypes with varying whole-arm chromosomal rearrangements.
• To understand the molecular features and nature of chromosomal rearrangements within and between species.
• To explore the role of these rearrangements in differentiation and integration processes during karyotype evolution.

Main Methods:

• Utilized telomere DNA fluorescence in situ hybridization (tDNA-FISH) to detect telomeric repeats.
• Analyzed G-banded metaphase chromosomes from representatives of the genera Sorex and Stenocephalemys.
• Employed fluorescein-conjugated peptide nucleic acid probes and 5'-TAMRA-labeled (CCCTAA)4 oligonucleotides.

Main Results:

• Detected both regular terminal and interstitial telomeric sequences (ITSs) in the studied mammalian karyotypes.
• Observed ITSs in a shrew specimen (Sorex) corresponding to a natural interracial F1 hybrid, identifying new race-specific metacentrics.
• Revealed species-specific tandem fusion rearrangements in Stenocephalemys autosomes and ITSs in pericentromeric regions of X chromosomes.

Conclusions:

• Telomeric signal distribution on mitotic chromosomes is heterogeneous and involved in mammalian whole-arm chromosomal variation.
• Robertsonian polymorphism and tandem fusions represent two models of karyotype evolution.
• Centromeric ITS signals likely indicate cytogenetic relatedness within species (races) or between species, rather than taxa differentiation.