Box-and-whiskers plot of the percent of sequence in each class of repeat element in (a) imprinted clusters (n = 19 covering 131 genes) and (b) the entire genome of each species. Repeat sequences that had significantly different proportions in the platypus from all therian genomes are marked by double asterisks. Boxes indicate the interquartile range with whiskers showing the full range for each data set. Black lines within boxes indicate the median value. There are significantly fewer LTR and DNA elements across the platypus orthologous imprinted regions compared to all other mammalian species. Chicken has noticeably fewer total repeats and no SINEs or small RNAs. C, chicken; D, dog; H, human; M, mouse; O, opossum; P, platypus. LINE, long interspersed nuclear element.