I don't know anything about DNA files, but I wonder how gzip (deflate) would fare if one of the non-default compression strategies were used. e.g. the RLE stra

I don't know anything about DNA files, but I wonder how gzip (deflate) would fare if one of the non-default compression strategies were used. e.g. the RLE strategy is good for data with many compressible patterns, while the filtered or Huffman-only strategies are good for data with few compressible patterns. The default strategy is a balance between the two extremes, which isn't tuned for a specific kind of input.