| Author/Editor | Lovšin, Nika | |
| Title | Molekularna evolucija non-LTR retrotranspozonov pri vretenčarjih | |
| Type | monografija | |
| Place | Ljubljana | |
| Publisher | Medicinska fakulteta | |
| Publication year | 2003 | |
| Volume | str. 121 | |
| Language | slo | |
| Abstract | Eukaryotic genomes contain large numbers of transposable elements (TE) that play crucial roles in genome evolution. Among the most widespread and ancient classes of TEs are non-LTR retrotransposons. In vertebrate genomes, representatives of six Glades are known: CR1, Ll, R4, L2, Rex1 and RTE. Bov-B and LINE2 elements have been studied in reptiles and LEVE-1 elements were studied in mammals, however, nothing is known about the origin and the evolutionary dynamics of CRl, L1 and LINE2 retrotransposons. In this thesis, the evolutionary dynamics of CRl, LINE2 and L1 non-LTR retrotransposons in vertebrates has been examined. Non-LTR retrotransposons are vertically transmitted from parents to offspring, but horizontal transfers are very rare. The distribution of CRl, L1 and LINE2 elements has been examined, both by PCR analysis and by searching databases. A region containing the reverse transcriptase domains (3. to 8. segment) of CRl, Ll and LINE2 retrotransposons has been amplified and sequenced from the genomes of 59 vertebrates. The presence of LINE2 in reptiles, amphibians, fishes and mammals reveals the widespread distribution of LINE2 in vertebrates. It was also found in protostomes. So we presume that the LINE2 element was present in the common ancestor of Protostomia and Deuterostomia and retained in different lineages over a long period of time (890 MY). The absence of LINE2 in turtles, birds, crocodiles and some representatives of mammals and the results of sequence analyses of vertebrate LINE2s indicate that the evolutionary dynamics of LINE2 is complex. Active copies are present in teleost fishes. The predominance of inactive LINE2 elements in Amniota indicates that they are in the phase of vertical inactivation. In birds, turtles and some mammals, L1NE2 appears to be in the phase of stochastic loss. (Abstract truncated at 2000 characters) | |
| Descriptors | DNA INSERTION ELEMENTS EVOLUTION, MOLECULAR VERTEBRATES GENOME TRANSFORMATION, GENETIC ESCHERICHIA COLI PLASMIDS BASE SEQUENCE AMINO ACID SEQUENCE POLYMERASE CHAIN REACTION CLONING, MOLECULAR PHYLOGENY |