Transposable elements Flashcards
what is a transposable element? is it inheritable?
“mobile DNA” that can ‘jump’ around the genome and copy itself
Can lead to a change or block of expression of nearby genes
acts like a parasite, often cause more harm than good
inheritable to >50% of offspring
what are the types of transposable elements?
class I–> copy and paste RNA retrotransposons
class II–> cut and paste DNA retrotransposons
which class of TE uses an intermediate to spread?
copy and paste RNA retrotransposons (class I)
what are the two types of copy and paste RNA retrotransposons (class I)
LTRs (long terminal repeat elements)
Non-LTRs eg LINEs ( long interspersed nuclear elements)
briefly explain LTRs mode of action.
1)TE transcribed and exported to the cytoplasm– RNA template made
2) tRNA binds at 5’ priming site, and TE is transcribed towards 3’ (some steps involved)
3) RNA template degraded by RNAseH.
4) new strand used as template and 3’ to 5’ transcription occurs
5) once synthesis is completed, enters the nucleus with INTEGRASE and can attack DNA
briefly explain LINEs mode of action.
1)TE transcribed and exported to the cytoplasm– RNP made (ribonucleoprotein particle)
2) one strand cleaved and annealed by mRNA retrotransposon, new DNA synthesised
Can result in the completion of synthesis –DUPLICATION or
degradation of non-homologous ends–> DELETION
briefly explain cut-and-paste transposons (class ii)– mariner transposition and P-elements
transposons excised from DNA sequence (staggered cuts) and insert themselves into another part of the genome
DNA repair synthesis fills the gaps
what are two other cut-and-paste mechanism examples?
helitrons and polintons
what similarities do LTRs and retroviruses have in common?
- same genes in same order
- replicate in the same way
what distinguishes LTRs and retroviruses?
LTR elements are not horizontally transmitted
