Time lapse: A glimpse into prehistoric genomics
Darren K. Griffin, Denis M. Larkin, Rebecca E. O'Connor
This study is brief introduction to the reconstruction of ancestral
karyotypes in extant species, specifically theropod dinosaur lineage using extant
avian chromosome level genome assemblies. This allows for a “complete” reconstruction to
occur (chromosome level). Genomic structure is the way that genes are arranged
on chromosomes and is species specific.
They used ancestral genome reconstruction tools Multiple Genome
Rearrangement and Analysis MGRA, to identify nineteen contiguous ancestral
regions (CARs). These were then used to compare the diapsid ancestor and chicken
genomes.
They first determine the likely karyotype of the avian ancestor
that would be most similar to a chicken or turkey. They then found the most
likely karyotype for this ancestral bird-lizard and the chromosomal changes
that took place between now and then. Several translocations and inversions (two
main changes) took place from a lizard-like genome structure to that of
soft-shelled turtles (275-255 mya). Due to the karyotypic similarities, there
were few changes from this early ancestor to the beginning of dinosaurs and
pterosaurs, to the theropod lineage and to modern birds. This shows that was an
avian-like karyotype in place roughly 240 mya. After the Chicxulub meteor,
there was an increased period of avian speciation with 36 lineages appearing
over 10-15 million years.
The avian-like karyotype has many micro chromosomes that allows
for variation through random segmentation and recombination. The authors
believe that this driver of natural selection allowed for dinosaurs to survive
multiple extinction events, becoming more diverse and speciose over time. This
paper briefly reviews the genome organization and evolution of ancient
chromosomes and their impact on phenotypic diversity, evolution, and adaptation.
18 February 2020 Potluck
Griffin, D. K., Larkin, D. M., & O’Connor, R. E.
(2019). Time lapse: A glimpse into prehistoric genomics. European Journal of
Medical Genetics, 63(2), 103640.
https://doi.org/10.1016/j.ejmg.2019.03.004
No comments:
Post a Comment