All reptiles such as alligators have temperature-dependent sex-determination (sex of the embryo is only determined by the incubation temperature, and not by genetic differences as in mammals and birds).
Many early efforts in genome sequencing are far from perfect. Usually, the initial genome sequence is called draft, and is intended as a first analysis to understand genome architecture. Improved genome assemblies have much utility, for example offering the ability of broader and long-range comparisons as well as analysis of repeats (e.g., mobile elements).
Rice et al. have generated an improved genome assembly of the American alligator (Alligator mississippiensis). The authors generated 210 million paired-end reads with the Illumina HiSeq 2500 instrument, which were then assembled using Meraculous. The genome size became 2.16 Gb (size is ~67% of the human genome), and showed longer continuity than the previous assembly from 2015.
Comparisons with the chicken genome revealed conservation of the estrogen-signaling pathways, indicating an important role of estrogen signaling even in a species without sex chromosomes.
Alligator genome resources
- GCA_000281125.4 (the new genome assembly)
- The Crocodillian Genomes Project
- Green et al., Science (2014) (the original draft genome sequence)