Mobile DNA Elements Flashcards
(24 cards)
what is the mobilome?
the fraction of genome containing all mobile genetic elements that can be transmitted through horizontal gene transfer
what are the mobile genetic elements?
plasmids
bacteriophages
transposons/ IS elements
what are insertion sequences?
simplest form of MGE
encode for transposase gene and contain inverted repeats at both ends
how are insertion sequences transferred?
horizontal gene transfer
what are transposons?
MGEs larger than IS elements
possess inverted repeats and have proteins encoded
what proteins are encoded in transposons?
transposases, endonucleases, accessory genes
example of a bacterial DNA transposon?
carry antibiotic resistance genes to confer resistance
what is transposition?
the process of genetic recombination that mobilises genetic elements from one DNA site to another
what are retrotransposons?
recombination involving a transient RNA intermediate and retro transcription into cDNA
what happens when transposons transpose within regulatory regions?
change gene expression
what are the transposon families?
DNA transposons
Virus like retro transposons
poly A retro transposons
what is the structure of DNA transposons?
flanked by 2 inverted repeats (recombination sites) and a gene encoding a transposase remain as DNA throughout recombination
what are virus like retro transposons?
flanked by 2 LTRs and region encoding for an integrase and reverse transcriptase
what are poly A transposons?
flanked by 5’ and 3’ UTR and a polyA
encodes for RNA binding protein and reverse transcriptase enzyme
what is the difference between transposons and retrotransposons?
transposons involved the cleavage and rejoining of DNA
retro transposons move to new DNA location using transient RNA intermediate
what does transposon Tn7 encode for?
a protein TnsA with restriction endonuclease activity at ends of transposon
TsnB and TsnA excise the transposon from its target site
what do transposons Tn10R encode for?
transposase that recognises the terminal inverted repeat sequence of IS10R, IS10L and Tn
what does transposon TS10L do?
similar sequence to IS10R but does not encode a functional response
how does Tn10 limit its copy number?
using antisense RNA to control the expression of the transposase gene
what 2 groups can poly A retrotransposons be classified into?
autonomous LINE or non autonomous SINE
what is the difference between autonomous and non autonomous poly a retrotransposons
autonomous encode for genes required to their own mobility and proteins
non autonomous cannot self promote
how does a LINE transposition occur?
reverse splicing
how can retrotransposons be identified in eukaryotes?
they lack introns due to integration of cDNA from processed mRNA
what can pseudogenes be caused by?
point mutations
homologous recombination
retrotransposition
