BIOL 300 Discussion Mobile Genetic Elements

Are transposons found in prokaryotes or in eukaryotes?

Both; first found in bacteria

What are several possible mutations caused by transposons?

Gene distruption when inserted in an important gene

Can transposons infect other hosts other than a host in which they are found?

No

Can transposons make copies of themselves?

Yes

Can transposons move from one location to another within the same genome?

Yes

What is the difference between a retrovirus and other DNA or RNA viruses?

Retroviruses have reverse transcriptase and includes RNA/DNA in its life cycle

Why is the DNA stage necessary in the retrovirus life cycle?

In order to integrate itself into host

What is a difference between (+) and (-) strand of viral RNA?

Message is (+) while template is (-)

What serves as a primer for RTase during retroviral infection?

tRNA

What enzyme is required for the integration of a dsDNA retroviral genome into the host genome?

Integrase

What is an additional gene that could be carried by a retrovirus?

Genes to transform a normal cell to a cancer cell

Why can genes in a viral geneome quickly become mutated?

They go through transcription which does not have proof reading activity

When a retrovirus integrates into DNA, does it generate extra direct repeats just as transposons do?

Yes

What are the activities of RTase?

RNA (+) and DNA (-), RNA/DNA to dsDNA, and degradation of RNA (RNase H')

What are retrotransposons?

Genetic elements that can amplify themselves using RNA intermediate

What is the difference between a retrotransposon and retrovirus?

A retrotransposon cannot move from cell to cell or organism to organism

Where is RTase encoded in LTR retrotransposons?

Coded in retrotransposon

What is VPL?

virus like particle

it looks like a retrovirus but it cannot get out of cell b/c missing Env, protein for packaging and infection

If supplemented with extra enzymes, can a retrotransposon become a functional retrovirus?

Yes

How could SINES arise if they do not contain RTase? How are they converted back to DNA?

They need some sort of RTase

What are Alu elements? Why are they called Alu? What RNA are the Alu elements related to? How did Alu elements become so widespread in the genome?

SINES most well known b/c it contains restiction sites for Alu restiction enzyme.

75rRNA

75 have been reverse transcribed to DNA by some reverse transcriptase

What are some strategies that an organism uses to deal with transposons?

Silencing

1) Act on DNA directly by methylation of DNA (prevents transcription)

2) RNA interface

Are sequences for new transposition insertion random?

Not always, target sites can be chosen

can be a consensus sequence, or DNA structure

Are transposable elements common in many organisms?

Yes

Why are composite transposons called "composite?"

They contain other genes besides just transposons and flanked by IS

In most cases what proteins are responsible for choosing the target sequence for a transposon?

Transposase

Where is the gene for transposase located?

Within the transposon

What does it mean to be "autonomous?"

Contains genes for transcription

Can transposons exist in genomic DNA and plasmids?

yes

Can one organism have more than one type of transposon?

Yes

How are the ends of IS elements different from the target sequence?

Target sequences are direct repeats while IS terminal repeats are inverted

What is the differece between transposons and defective elements?

Transposons code for transposase

What is the result of the target sequence after transposistion?

Duplicated

Why is resolvase needed in replicative transposition?

Cointegrate is formed and nedds to be resolved

When a transposon is removed from one location and transposed to another, is the "cutting out" precise?

Not always, only a rare occurence

What is the difference between replicative and nonreplicative transposition?

Copy + paste; cut + paste

Insertion sequence

The simplest kind of transposable element, consisting of inverted repeats of DNA flanking a gene for transposase, the enzyme that catalyzes transposition.

replicative transposition

to copy and paste

nonreplicative transposition

to cut and paste

Genes inside of a virus

-gag

-polymerase

-env

Types of Transposons Chart

Transposition types chart

Replication be Nonreplicative Transposition

Genes inside of a virus

Reverse transcription

Retrotransposons Chart