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gene221 > Lecture 13 > Flashcards

Lecture 13 Flashcards

1
Q

True or False

Transposons are the most common genes in nature

A

TRUE

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2
Q

What % of the human genome do transposons make up?

A

50%

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3
Q

How do transposons move relative to the host recombination system?

A

Transposons move from one site in the genome to another independent of host recombination system

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4
Q

What do transposons cause?

A

Large amounts of spontaneous mutations and chromosomal rearrangments

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5
Q

What do transposons allow?

A

The rapid acquisition of multiple antibiotic resistances and facilitates flow of genes between species

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6
Q

What are the types of Bacterial Transposons?

A
  1. Insertion sequences
  2. Composite transposons
  3. Non composite transposons
  4. Conjugative transposons
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7
Q

Describe an Insertion Sequence

A

They are the simplest type of transposon and only encode protein needed for their own transposition

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8
Q

What is at the end of all Insertion Sequences?

A

Ends of all IS show Inverted Terminal Repeats of 20-50 bp’s

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9
Q

Describe a Composite Transposon

A
  • Consists of 2 IS elements either side of a central region carrying other genes e.g. antibiotic resistance
  • Insertion Sequences elements supply transposase and Inverted Terminal Repeats
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10
Q

Describe Non-Composite Transposons

A
  • They are simple

- Encode genes for own transposition and accessory functions, have inverted terminal repeats

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11
Q

Do Non-Composite Transposons rely on Insertion Sequences?

A

NO, they no not rely on Insertion Sequence modules for transposition

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12
Q

Which elements undergo conservative transposition?

A

Insertion Sequences and Composite Transposons

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13
Q

Describe Conservative transposition

A

‘Cut and Paste’

  • Transposase makes two cuts
    1. dsDNA cut in donor
    2. Staggered cuts in target
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14
Q

What happens to the Donor DNA in conservative transposition?

A
  • The donor DNA flanking sequence is either lost or repaired
  • A small direct repeat of the target DNA (DNA surrounding where the element has been added ) either side of transposon
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15
Q

Describe Replicative transposition

A

‘Copy and Paste’

  • Transposase make two cuts
    1. 2x ssDNA cuts in donor
    2. Staggered cuts in the target
  • Resolution of cointergrate requires resolvase
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16
Q

Which element undergo replicative transposition?

A

Non composite transposition

17
Q

What is resolvase?

A

A site specific recombination enzyme which separates the two molecules through a recombination event

(replicative transposition)

18
Q

What is a cointergrate?

A

Two molecules joined together, 2 copies of Transposon

19
Q

What is the end results of replicative transposition?

A

Original DNA molecule reformed + new DNA molecule with transposon in it

20
Q

Describe Conjugative transposons

A
  • They are able to excise from genome and transpose from one cell to another via a conjugative intermediate
  • They insert randomly into recipient and also reinsert into donor genome
21
Q

What are Conjugative transposons important for?

A

Important in spreading of antibiotic resistance and virulence mainly in gram positive bacteria

22
Q

Where do Conjugative transposons reside?

A

In bacterial chromosomes and carry lots of Antibiotic resistance

23
Q

Do Conjugative transposons have an Ori T?

A

Yes

24
Q

Can Conjugative transposons form a mating bridge?

A

Yes

25
Q

How are insertions formed (when looking at transposons)?

A

Through transposition or homologous recombination

26
Q

How are replicon fusions formed?

A

Through a process like Hfr formation

27
Q

How are deletions formed?

A

Through homologous recombination between two copies of a transposon present in DIRECT orientation
->they are rearranged in the same reading direction

28
Q

How are inversions formed?

A

Homologous recombination between two copies of a transposon present in inverted orientation
->read in opposite direction

gene221 (29 decks)

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