Question

^5. Describe the molecular mechanism that determines lysogeny or lysis of the host cell. What genes/proteins are involved? What determines if the cell exits lysogeny and enters the lytic cycle? Distinguish between early-immediate, early, and late gene transcription. What processes are occurring in these stages of transcription?

Answer 1

The molecular mechanism that determines the lysogeny or lysis of the host cell is the abundance of the phage that is present in an area as they possess the ability to  produce and sense small peptides in a process similar to that of quorum sensing.Also,the lytic-lysogeny decision depends on the levels of the lambda protein CII that are found within infected bacterium cell. While high levels results in little production of the CI repressor directing the lytic cycle.; at the same time lower levels of CII, by contrast, allows for the production of CI thereby directing to the  lysogenic cycle.

If a bacterial cell containing the prophage is exposed to environmental stressors like the UV light, low nutrient conditions or chemicals such as mitomycin C, then the prophage may undergo spontaneous extraction from the host genome and enter the lytic cycle in the  process known as induction.

Early immediate gene transcription involves transcription of those genes that are activated for a short time and rapidly in response to a wide variety of cellular stimuli that they are exposed to.Such type of gene transcription takes place in the first round of transcription before any new proteins are produced.Early gene transcription invloves the transcription of genes that produce non-structural proteins which go on to initiate replication of the genome and expression of late genes mostly in virus.Late gene transcription invloves transcription of genes that moslty produce structural proteins in virus.