L11 specialised transduction/transposition

What is generalised transduction

Transfer of any bacterial gene by bacteriophage

Which phage mediates generalised transduction

P1 phage

What determines which DNA is transferred in generalised transduction

Random packaging

What is cotransduction

Transfer of two genes together by phage

What does cotransduction frequency indicate

Gene distance

How are closely linked genes identified

High cotransduction frequency

What is the cotransduction size limit

About one hundred kilobase pairs

Why is cotransduction limited in size

Packaging capacity of phage

What is specialised transduction

Transfer of specific genes near integration site

Which phage mediates specialised transduction

Lambda phage

What are the two life cycles of lambda phage

Lytic and lysogenic

What happens first after lambda infection

DNA circularisation

How is lambda DNA circularised

Complementary ends anneal and ligate

What happens in the lytic cycle

DNA replication and phage production

What replication mechanism is used in lytic cycle

Rolling circle replication

What is a concatamer

Long DNA molecule of repeated genomes

What cuts concatamers into genomes

Ter enzyme

What sequence is recognised for cutting

Cos sequence

What happens in lysogenic cycle

DNA integrates into host genome

What type of recombination integrates lambda DNA

Site specific recombination

What sites recombine during integration

attB and attP

What is attB

Bacterial attachment site

What is attP

Phage attachment site

What is the core sequence in recombination

O sequence

What are attL and attR

Sites flanking integrated prophage

How is prophage normally excised

Recombination between attL and attR

What is aberrant excision

Incorrect removal of prophage

What happens during aberrant excision

Bacterial DNA is included in phage

What is lambda d phage

Defective phage carrying bacterial DNA

What gene is commonly transferred by lambda d

gal gene

Why cant defective phage complete life cycle

Missing essential genes

How does specialised transduction occur

Transfer of nearby bacterial genes

What limits specialised transduction

Proximity to integration site

What is transformation

Uptake of naked DNA

What happens to DNA in transformation

It recombines into genome

What is cotransformation

Uptake of two linked genes

What does cotransformation frequency show

Gene distance

What are transposable elements

DNA sequences that move in genome

Where are transposons found

All organisms

What effect do transposons have on genes

Can disrupt function

Do transposons require homology

No

What happens at insertion site of transposon

Target site duplication

What determines duplication length

Type of transposon

What are the main types of transposons

DNA only LTR and non LTR

Which transposons are in bacteria

DNA only

What is a DNA only transposon

Moves without RNA intermediate

What are terminal inverted repeats

Short repeated sequences at ends

What enzyme recognises inverted repeats

Transposase

What is an autonomous transposon

Encodes its own movement proteins

What is a non autonomous transposon

Depends on other elements

What are insertion sequences

Simple transposons encoding transposase

What do insertion sequences contain

Transposase gene and repeats

What are composite transposons

Genes flanked by insertion sequences

What do composite transposons often carry

Antibiotic resistance genes

What are non composite transposons

Independent transposons

What is an example of non composite transposon

Tn3

What is cut and paste transposition

Element excised and reinserted

What is nick and paste transposition

Element remains attached during transfer

What is a cointegrate

Joined donor and target DNA

How is cointegrate resolved

Into separate molecules

Can some transposons use both mechanisms

Yes

What is an episome

Plasmid that integrates into chromosome

How are Hfr strains formed

Recombination with chromosome

What sequences mediate integration

Insertion sequences

Is plasmid integration reversible

Yes

How can gene order be mapped by conjugation

Based on transfer timing

How can gene order be mapped by cotransduction

Based on frequency

How can gene order be mapped by cotransformation

Based on co uptake frequency

What scale does conjugation mapping cover

Whole chromosome

What scale does cotransduction mapping cover

Around one hundred kilobase pairs

What scale does cotransformation mapping cover

Around twenty kilobase pairs

What are auxotrophs

Mutants requiring nutrients

Why are bacteria useful for genetics

Easy to grow and manipulate

What are main gene transfer methods in bacteria

Conjugation transformation and transduction