transduction pt 8

What is transduction?

The transfer of bacterial DNA from one bacterium to another by a bacteriophage.

What are the two types of transduction?

Generalized transduction, Specialized transduction.

What is generalized transduction?

The transfer of potentially any bacterial chromosomal gene from one bacterium to another by a bacteriophage.

What type of bacteriophage can perform generalized transduction?

Virulent or temperate phages during the lytic cycle.

Why is generalized transduction considered a random process?

Because a bacteriophage may accidentally package different pieces of bacterial chromosomal DNA, so potentially any bacterial gene can be transferred.

What happens when a bacteriophage accidentally packages bacterial DNA instead of viral DNA?

A defective transducing particle is produced. It can transfer the bacterial DNA into another bacterium.

What is specialized transduction?

The transfer of only specific bacterial genes by a temperate bacteriophage.

What type of bacteriophage performs specialized transduction?

A temperate bacteriophage that has been in the lysogenic cycle and then enters the lytic cycle.

Why does specialized transduction only transfer specific bacterial genes?

Because only bacterial genes located near the prophage integration site are likely to be accidentally removed and transferred.

What is the difference between generalized and specialized transduction?

• Generalized transduction: any bacterial gene can be transferred because bacterial DNA is accidentally packaged during the lytic cycle.

• Specialized transduction: Only specific bacterial genes near the prophage integration site are transferred because of incorrect prophage excision.

What is the main difference between the mistakes that occur in generalized and specialized transduction?

• Generalized transduction accidentally packages bacterial DNA instead of viral DNA.

• Specialized transduction incorrectly removes viral DNA from the bacterial chromosome, taking nearby bacterial genes with it.

What is the difference between the lytic cycle and the lysogenic cycle?

• Lytic: Virus immediately reproduces, assembles new viruses, and destroys the host cell.

• Lysogenic: Viral DNA integrates into the host chromosome and is copied as the host cell divides without immediately destroying it.

What is the difference between naked and enveloped animal viruses?

• Naked: Capsid and nucleic acid only; no envelope.

• Enveloped: Capsid and nucleic acid surrounded by an outer membrane envelope.

What is the difference between cytocidal and budding viruses?

• Cytocidal: Release new viruses by destroying the host cell.

• Budding: Release new viruses by pushing through the host cell membrane, usually leaving the host cell alive.

What is the difference between positive-ss and negative-ss RNA viruses?

• Positive-ss RNA: Acts directly as mRNA and can be translated by ribosomes.

• Negative-ss RNA: Must first be copied into positive-ss RNA by viral transcriptase before ribosomes can translate it.

What is the difference between replicase and transcriptase?

• Replicase makes complementary RNA copies for genome replication,

• transcriptase produces positive-ss RNA from a negative-ss RNA template so it can be used as mRNA.

What is the difference between transformation and transduction?

Transformation: Bacteria take up free DNA from their environment. Transduction: Bacterial DNA is transferred by a bacteriophage.

What is the difference between conjugation and transformation?

Conjugation: DNA is transferred through direct contact between bacteria. Transformation: Bacteria take up free DNA from their environment.

What is the difference between generalized and specialized transduction?

Generalized: Any bacterial gene can potentially be transferred. Specialized: Only specific genes near the prophage integration site can be transferred.

How does generalized transduction begin?

A bacteriophage injects viral DNA, causing the bacterial chromosome to break into pieces.

What happens during generalized transduction assembly?

A piece of bacterial DNA is mistakenly packaged into a viral capsid instead of viral DNA.

How is bacterial DNA transferred during generalized transduction?

The defective phage injects the bacterial DNA into another bacterium.

What can happen to transferred DNA during generalized transduction?

It may recombine with the recipient bacterium's chromosome.

How does specialized transduction begin?

Viral DNA integrates into the bacterial chromosome during lysogeny.

What happens when a prophage leaves the chromosome?

During induction, viral DNA may be removed incorrectly, taking nearby bacterial genes with it.

How are bacterial genes transferred in specialized transduction?

A phage packages the bacterial genes and transfers them to another bacterium during infection.

What makes specialized transduction different from generalized transduction?

Specialized transduction transfers only specific bacterial genes near the prophage integration site.