Question

– Bacterial transcription can be controlled by repressors and activators. Define repressor and explain the repression mechanism.

- Why are non-enveloped viruses generally more resistant to disinfectants than are enveloped virus?

- Why are RNA viruses and retroviruses more error-prone in their replication than DNA viruses?

-What is the role of prophages in persistent infections of bacterial cells?

- What is the role of provirus in persistent infections of animal cells?

Answer 1

1. Repressors are mainly used in the negative regulation where the repressors bind to the operator region near promoter which stops transcription process.

The repression mechanism can be explained by lac operon where in case of lac repressor acts as a repressor .

In the presence of glucose and lactose availability in medium for the bacteria there is no need for the transcription of the lac operon because there is ready mate availability of glucose because of which the repressor binds to the operator region there by stopping transcription.

2. Non enveloped virus are viruses which contains capsid as an outer coat which is made up of proteins .But enveloped viruses do not contains they are easily lysed due to the rupturing of outer membrane . Capsid is a solid substance resist to various factors it cannot be breaked easily so it is more resistant then enveloped virus.

3. RNA viruses and reteroviruses are more error prone because during replication of the the RNA is converted to the DNA by reverse transcriptase to integrate into host genome and replicate during this time there is a high chance of errors where DNA is directly replicated so there are less errors.

4. Prophage is a bacteriophage which is a virus which infects bacteria . The viral genome is integrated into the bacteria where the RNA as a genetic material integrates into host genome and they become latent that is transcriptionally inactive after sometimes they replicate there genome and join the other transcription process of bacteria and silently damage host cell.Due to which they can infect many bacteria and cause peristant infections.

5. Unlike prophage, proviruses are the type of viruses which infects animal cells which are the viruses same as prophage, which also infect animal cells slowly .for example HIV viruses is a proviruses