Science diary

Define retrotransposons with example. Class 1 transposons also known as retrotransposons move through the active RNA intermediaries. In other words, class 1 Te1 do not encode transposase, rather they produce RNA transcripts and then relay upon reverse transcriptase enzymes to reverse transcribe the RNA sequence back into which is then inserted into target site. There are two types of class 1 Te s 1) LTR ( long terminal repeat): LTR retrotransposons are characterized by the presence of long terminal repeats on both ends of LTR retrotransposons and DNA transposons are only ancient genomic relics and are not capable of jumping. Eg: Human endogenous retroviruses and various Ty elements S cerenisione. 2) Non LTR retrotransposons:  Non LTR Te s, lack the repeats and include both autonomous and non-autonomous members. Autonomous Non LTR retrotransposons include LINES (long interspersed nuclear elements). In mammals non LTR retrotransposons are the most common type of mobile elements. Line 1 o

Define Prokaryotic transposons with diagram. Although the presence of transposons was predicted in Eukaryotes but first observation at molecular level was done in bacteria. Which is a Prokaryote. Bacterial transposable elements are of following types: A) Insertion sequence or I s elements: They are the transposable sequence which can insert at different sites in the bacterial chromosomes.  I s  elements contains ITRs (inverted terminal repeats) these were first observed in E.coli. The term ITRs implies that the sequence at 5' end of one strand is identical to the sequence at 5' end of the other strand but they run in opposite direction. B) Prokaryotic transposon element: These are also called composite transposons and are shown by symbol "Tn".  These are large transposons which are formed by capturing of an immobile DNA sequence within two insertion sequences thus enabling it to more. Eg:  Tn1, Tn5, Tn9, Tn10, etc..

M phase inducer phosphatase 1 also know as dual specificity phosphatase CDC 25A is a protein that in humans encoded by cell division cycle 25 homolog A (Cdc 25A)  gene. It is a member of the Cdc 25 family of dual specificity phosphatases. Cdc 25A is required for progression from G1 to the S phase of the cell cycle.  Plays role in later cell cycle events. In particular it is stabalised in metaphase cells and is degraded upon metaphase exit  akin to  cyclin B. It is competent to activate G1/S cyclin dependent kinases Cdk 4 and Cdk 2 by removing inhibitory phosphatase groups from adjacent tyrosine and theronine residues.  It can also activate Cdc 2 (cdk 1) the principal mitotic cdk. Cdc 25A is specifically degraded in response to DNA damage, resulting in cell cycle arrest.