Transposable Elements Flashcards
DNA sequences that can move within the genome
transposable genetic elements
enzyme-driven process that moves transposable elements
transposition
transposition is a – event that has a biological basis
mutational
transposition typically create mutations by inserting themselves into wild-type alleles
insertional inactivation
genetic element that was located at the site of chromosome breakage
dissociation (Ds) element
chromosome breakage at Ds was activated by an unlinked genetic element,
activator (Ac) element
the transposable element (central region) itself is flanked by
terminal inverted repeats
the inserted transposable element is bracketed by
flanking direct repeats
Flanking direct sequence is generated by – as part of the insertion event
DNA polymerase activity
transpose through an RNA intermediate
retrotransposons (class I)
transpose as DNA sequences
DNA transposons (class II)
T/F: all DNA transposons carry the transposase gene that produces the transposase enzyme required for the movement of the transposon
true
retrotransposons are composed of – but they are transcribed into RNA before transposition, and the RNA transcript is then copied back into DNA by reverse transcriptase
DNA
the – is then inserted into a new location, where flanking direct repeats are formed
reverse-transcribed DNA
T/F: retrotransposons are found in bacteria
false
always generate new copies of themselves for transposition
retrotransposons
T/F: DNA transposons found in bacterial, archaeal, and eukaryotic cells
true
bacterial transposition = – transposition only
DNA
transposon has terminal inverted repeats surrounding the transposase gene with no other genes present
simple transposons
simple transposons in bacteria are identified as
insertional sequences
contain two insertion sequences and one or more additional genes
composite transposons
copy and paste = increase in number
replicative transposition
cut and paste = same number
nonreplicative transposition
retrotransposon transposition mechanism
replicative transposition
DNA transposition mechanism
replicative or nonreplicative transposition
simple DNA sequences that contain only the genetic info necessary for their own transposition
insertion sequences
transposition of an IS element → formation
FDR
transposition of IS element can produce mutation by inserting IS element into a
gene or regulatory sequence
IS regions are potential sites of – between bacterial chromosomes and plasmids forming Hfr chromosomes
recombination
IS elements promote recombination that can lead to –
gene transfer
T/F: all identified transposable elements in archaeal genomes are IS type
true
example of composite transposon
Tn10
bacterial composite transposons (Tn) are composed of two copies of an –, each flanked by its TIR sequences, and one or more additional genes
IS element
T/F: Tn are longer than IS elements
true
additional genes in Tn elements are variable and are contained in the – that flanked by 2 IS elements
central region
example of Noncomposite transposons
Tn3
do not contain insertion sequences but do carry additional genes
noncomposite transposons
noncomposite transposons transpose similar to –
composite transposons
½ of human genome =
transposable elements
Ac/Ds elements and P element =
DNA transposons
more commonly eukaryotic transposable elements such as the human genome =
retrotransposons
combination of sterility, high mutation rate, and a propensity chromosomal aberrations and nondisjunction
hybrid dysgenesis
retrotransposons encode reverse transcriptase (–) to catalyze transposition
pol
retrotransposons contain pol and gag but not –
env
gene(s) carried by retrotransposons are flanked by – that may be up to several 100s bp
long terminal repeats (LTRs)
examples of retrotransposons
Ty elements in yeast
copia elements of Drosophila
LINE and SINE elements of humans
All of the following are characteristics of insertion sequences elements except _______.
- they are flanked by inverted repeats
- they encode protein
- there can be more than one copy of an IS element in a bacterial genome
- a copy of the insertion sequence becomes integrated at a new location
a copy of the insertion sequence becomes integrated at a new location
(The insertion sequence itself, not a copy, is excised from its original location and transferred to a new one.)
IS elements contain the gene encoding –
transposase
The role of transposase activity in IS element transposition includes _______.
cutting DNA at the target sequence
transposes makes staggered cuts at the site targeted for insertion
Which of the following transposition events is most likely to result in a loss of function mutation?
- Transposition of an IS element that contains a stop codon within the inverted repeat sequence
- Insertion near the promoter region of a gene
- Insertion of an IS element within the coding region of a gene
Insertion of an IS element within the coding region of a gene (Insertions of DNA elements within coding regions have the greatest potential for altering amino acid sequence and/or causing truncation of a polypeptide due to frameshift.)
What sequences or structures within the DNA can be used to identify sites of transposition?
- target site duplication and direct repeats
- target site inversion and direct repeats
- chromosome translocation and insertion of transposase gene
- target site duplication and short tandem repeats
- inverted loops
target site duplication and direct repeats
What evidence suggests that copia elements of fruit flies and Ty elements of yeast are related to RNA-containing viruses?
- They all contain gag genes.
- They all contain pol genes.
- They all have long terminal repeats at their ends.
- They are present in the form of RNA sequences in cells.
- They use reverse transcription for insertion into host chromosomes.
- They all cause mutation by insertion.
- They all contain env genes.
- They all contain gag genes.
- They all contain pol genes.
- They all have long terminal repeats at their ends.
- They use reverse transcription for insertion into host chromosomes.
Which of the following statements about an R factor is false?
- Encodes multiple drug resistant genes.
- Encodes genes that induce lysis of the bacterial cell.
- Can be propagated horizontally through a bacterial population.
- Encodes the genes required for conjugation.
- Encodes genes that induce lysis of the bacterial cell.
