L23 Transposable Elements Flashcards
what did Barbara McClintock discover?
that DNA moves around on chromosomes!
transposable elements are…
DNA sequences that move within and between chromosomes
where are TEs found?
in ALL organisms
what percent of human chromosomal DNA do TEs comprise?
45%
TEs contribute to 3 things…
1) spontaneous mutation
2) genetic rearrangements
3) horizontal transfer of genetic material
3 ways to classify TEs
DNA vs RNA
viral vs non-viral
replicative mechanism vs excision mechanism
2 modes of transposition
Class I - copy and paste
Class II - cut and paste
Class I has blank while Class II does not
an RNA intermediate
DNA transposons move their location without…
going through RNA intermediate stage (Clas II)
what’s located at ends of TEs?
inverted terminal repeats (ITRs)
ITRs are recognized by…
transposase
blank codes for transposase
open reading frame
an open reading frame is required for…
movement of TE in and out of genome
direct repeats are NOT part of… they are merely…
transposon; footprints of transposition
transposase is encoded by…
TE (autonomous) OR from another TE (non-autonomous)
transposase binds to…
both ends of transposon, which consists of ITRs
DNA at the target site is cut in an offset manner at…
the sticky ends
after the transposon is ligated to the host DNA, the gaps are…
filled in with complementary direct repeats
Class I transposition have…
an RNA intermediate
Class I TEs utilize…
reverse transcriptase
Class I TEs resemble…
retroviruses
2 types of Class I retrotransposons
LTR (long terminal repeats) and non-LTR
retrotransposons are all…
type I TEs
a retrovirus can turn into an…
LTR retrotransposon
a retrovirus can turn into an LTR retrotransposon if the gene for the…
envelope protein is damaged
the LTR is the…
control center
LTR consists of 3 regions…
U3 region
R domain
U5 region
U3 region contains the…
enhancer and promoter sequences necessary for transcription
R domain encodes the…
5’ capping sequences (5’ cap) and the poly-A (pA) signal
U5’s purpose is unclear, but it may aid in…
polyadenylation
5’ LTR and 3’ LTR are NOT…
inverted
2 main LTR retrotransposon genes
gag & pol
gag (group-specific antigen) makes up the…
inner shell of the viral coat
pol encodes 3 proteins…
reverse transcriptase
integrase
protease
protease function
cleaves the products of these genes into separate units
non-LTRs contain 1 or 2…
ORFs
non-LTRs contain genes for…
reverse transcriptase, RNA-binding protein, nuclease, and sometimes ribonuclease H domain
following transcription and nuclear export, the ORFs are translated and assemble to form…
a ribonucleoprotein particle (RNP)
after translation, what happens to RNPs…
they are placed back into the nucleus and then integrated into the chromosomes
2 types of non-LTR retrotransposons
1) long interspersed nuclear elements (LINEs)
2) short interspersed nuclear elements (SINEs)
LINEs make up roughly % of the human genome
21%
LINEs are ~ how many BPs long?
7000 BPs
SINEs are how many BPs long?
100-700 BPs
SINEs are all non-autonomous and rely on…
LINEs
SINE RNAs form a complex with LINE proteins and are inserted into the genome by…
target primed reverse transcription
hemophilia A is a disease caused by…
LINEs inserted at 2 points within a gene
a study showed LINE was not on mother’s X chromosome but on…
both parents’ chromosome 22
TE insertion in coding region causes…
translation disruptions
TE insertion in intron causes what 2 things…
1) termination signal can terminate transcription
2) splicing of RNA transcribed from a gene
TE insertion in gene’s transcription regulator region effects…
gene expression
TE insertion in identical TEs in genome causes the potential for…
transposon recombination
TEs contribute to evolution by…
altering genes and chromosomes
in Drosophila, LINE-like elements evolved to…
act in telomeres
