Genomic FeaturesThe new genome sequences confirmed that birds have unusually small and fragmented genomes compared to other vertebrates, a characteristic that the authors suggest might be due to the erosion of junk DNA, as well as loss of functional genes. However, they also found that bird genes tended to be very short. In fact, protein-coding genes in birds are on average 30 – 50% shorter than genes in reptiles and mammals. Birds achieve this by having denser genes. Genes contain ‘introns’, which don’t directly code for a protein, but are important in gene regulation, and a process called alternative splicing which allows one gene to code for multiple related proteins. Birds tend to have smaller introns and shorter regions between their genes.
Interestingly, one mammal group shows a very similar trend – bats. Therefore it seems likely that short, dense genes and smaller regulatory regions may be an adaptation to flying – Zhang and colleagues suggest it may facilitate more efficient gene regulation, necessary to meet the power demands of flight.
原文中的第二段，明确的出现了“蝙蝠”的例子，说蝙蝠也有short gene, 但是它是用来支持"short genes may be an adaptation to flying"这个观点的.
而原题中，想要论证和支持的是，这个结论是错误的。所以考古答案1：蝙蝠也有short gene，明显是在削弱原题的结论了。
