Squamate Chromosome Size and GC Content Assessed by Flow Karyotyping

Abstract

Chromosome homologies in reptiles have been investigated extensively by gene mapping and chromosome painting. Relative chromosome size can be estimated roughly from conventional karyotypes, but chromosome GC content cannot be evaluated by any of these approaches. However, GC content can be obtained by whole-genome sequencing, although complete data are available only for a limited number of reptilian species. Chromosomes can be characterized by size and GC content in bivariate flow karyotypes, in which the distribution of peaks represents the differences. We have analysed flow karyotypes from 9 representative squamate species and show chromosome profiles for each species based on the relationship between size and GC content. Our results reveal that the GC content of macrochromosomes is invariable in the 9 species. A higher GC content was found in microchromosomes, similar to profiles previously determined in crocodile, turtle, and chicken. The findings suggest that karyotype evolution in reptiles is characterized by unique features of chromosome GC content.

Robertsonian fusion triggers recombination suppression on sex chromosomes in Coleonyx geckos

“…The karyotype of C. mitratus was identical to the previously known karyotype of C. elegans 23 , in accordance with their sex chromosome identity 24 and similarity of ow-sorted karyotypes 41 . The degenerate parts of the C. mitratus and C. elegans Y chromosomes are homologous to a part of the chicken chromosome 11 (GGA11, homologous to ACA8), small proximal part of chromosome 6 (GGA6), and small median part of chromosome 1 (GGA1) as was shown in the previous study based on different technique, i.e.…”

“…Flow-sorted chromosome libraries and FISH Flow sorting of C. elegans chromosomes has been previously described 23,41 . Painting probes were ampli ed by DOP-PCR ampli cation of ow sorted chromosomes and labeled with biotin-dUTP and digoxigenin-dUTP (Sigma) by secondary DOP-PCR ampli cation as described previously 42 .…”

Shedding light upon the complex net of genome size, genome composition and environment in chordates

“…A difference between cheloniids/crocodiles and squamates is the presence in the latter of two types of chromosomes: microchromosomes, richer in genes, and macrochromosomes (Kasai et al 2019).…”

Observations on chromosome-specific sequencing for the construction of cross-species chromosome homology maps and its resolution of human:alpaca homology

“…Chromosome sorting also allows the measurement of individual chromosome size in any species and thus estimates of genome size from summation of chromosome sizes; the method requires the joint sorting of mixed chromosome preparations from test and control species in which some chromosome sizes are known in the latter. The procedure has been published in studies used to estimate genome sizes in examples of mammalian [ 10 ], marsupial [ 11 ], avian and reptilian [ 12 , 13 ] species. Our methods for chromosome sorting, DNA amplification and in situ hybridization are fully described in these reports [ 12 , 13 ] and are not repeated here.…”

“…The procedure has been published in studies used to estimate genome sizes in examples of mammalian [ 10 ], marsupial [ 11 ], avian and reptilian [ 12 , 13 ] species. Our methods for chromosome sorting, DNA amplification and in situ hybridization are fully described in these reports [ 12 , 13 ] and are not repeated here.…”