Ubiquitous mammalian-wide interspersed repeats (MIRs) are molecular fossils from the mesozoic era

Distribution of the mammalian-wide interspersed repeats (MIRs) in the isochores of the human genome.

The distribution of MIRs (mammalian-wide interspersed repeats) was investigated in 164 human sequences (> or = 100 kb), which were assigned, according to their GC level, to isochore families L, H1, H2 and H3. MIR elements, whose total number in the genome was estimated to be about 3.3 x 10(5), were found to be unevenly distributed in human isochores. The majority of MIRs (55%) were found in the...

Large-scale analysis of exonized mammalian-wide interspersed repeats in primate genomes.

Transposable elements (TEs) are major sources of new exons in higher eukaryotes. Almost half of the human genome is derived from TEs, and many types of TEs have the potential to exonize. In this work, we conducted a large-scale analysis of human exons derived from mammalian-wide interspersed repeats (MIRs), a class of old TEs which was active prior to the radiation of placental mammals. Using e...

Appendix 1 List of fossils, described as new by Senowbari-Daryan et al. from the Permian and Mesozoic of Iran

Genomic evidence for large, long-lived ancestors to placental mammals.

It is widely assumed that our mammalian ancestors, which lived in the Cretaceous era, were tiny animals that survived massive asteroid impacts in shelters and evolved into modern forms after dinosaurs went extinct, 65 Ma. The small size of most Mesozoic mammalian fossils essentially supports this view. Paleontology, however, is not conclusive regarding the ancestry of extant mammals, because Cr...

MIRs are classic, tRNA-derived SINEs that amplified before the mammalian radiation

Short Interspersed Nucleotide Elements (SINEs) are highly abundant in mammalian genomes. The term SINE has come to be restricted to short retroposons with internal RNA polymerase III promoter sites in a region derived from a structural RNA (usually a tRNA). Here we describe a novel, 260 bp tRNA-derived SINE, some fragments of which have been noted before to be repetitive in mammalian DNA. Unlik...