From “Chromosomes’ Big Picture: Similarities Found in Genomes Across Multiple Species; Platypus Still out of Place” (ScienceDaily, July 11, 2011), we learn:
“Basically what this all means is that if the chromosome number of a species can be given, the relative sizes of all the chromosomes can instantly be known,” Yu said. “Also, if you tell me the genome size in the chromosome base pair, I can tell you the base pair length of each chromosome.”According to Yu, the most surprising finding is the extremely consistent distribution pattern of the chromosomes, a result from comparing the full sets of chromosomes — called genomes — of the 68 random eukaryotes. The team found that nearly every genome perfectly formed an S-curve of ascending chromosomal lengths when placed on a standardized X-Y axis. That meant the genome from a species of rice expressed the same pattern as the genome from a species of maize, sorghum, fruit fly, dog, chimpanzee, etc.
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The only genomes that deviated from forming an S-curve were that of the platypus — an organism that contains characteristics of birds, reptiles, mammals, amphibians and fish — and those of birds. Birds are unique because in addition to their usual chromosome sequences, they contain one additional set of minichromosome sequences, according to Zhongwei Lin, research associate in agronomy.
But then, any scheme that successfully incorporated the platypus would certainly be wrong.
The deviations (birds, platypus) show that the pattern isn’t essential for life, just practical for life. A fundamental grammar rule? The platypus exception gives one pause for thought: Did extinct life forms also show this S-form pattern or no?
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