TBR test 2 biological sciences q 136

[2010premed]

In Figure 1, the latent period is longer than the eclipse period, because:

A. it takes longer to assemble phages in the latent period than it does in the eclipse period.
B. the phage lysozyme is synthesized late in the infection cycle.
C. viral DNA replication proceeds more rapidly in the eclipse period than in the latent period.
D.

the phages in the extracellular suspension need more time to adsorb to their bacterial hosts.
answer: B

I'm a bit confused about the graph (see below) what exactly is the eclipse period?

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[firecloak]

The graph is about when a bacteriophage infects bacteria. When the bacteriophage lands on the bacteria's cell wall, it injects its nucleic acid into the bacteria. After that, the capsid remains on the surface of the bacteria. It doesn't fall off right away; it just stays there for several minutes.

When hundreds of bacteriophage infect a bacteria, all the bacteriophages leave their capsids on the outside, effectively leaving a black outline around the bacteria. This black outline is called an "eclipse".

 

[2010premed]

So B is right basically b/c if lysozyme shows up too early, the bacteriophages won't be able to destroy the bacteria b/c they won't have reached the end of the eclipse period, and therefore won't all have appeared on the cell.

Do you know why A is wrong?

 

[firecloak]

The graph is talking about a bacteriophage in the lysogenic cycle.

3 things happen once a bacteriophage attacks a bacteria:
1) Attachment
2) Eclipse
3) Lytic or Lysogenic (latent) cycle

The latent period is the time when the phage's DNA is incorporated into the host DNA. At this point the phage remains inactive, so it doesn't do anything. The phage doesn't assemble in the latent period; it just stays within the host DNA, that's why A is wrong. Whenever the host cell divides, it makes a copy of the phage DNA too. This cycle can last a long time. Usually it ends when the bacteria is under some sort of stress.

Some time later, the bacteriophage enters the lytic cycle. Then the phage makes its viral proteins. After that, it makes a lysozyme, which destroys the bacteria cell wall as it leaves.

If it makes the lysozyme too early in the cycle, then the bacteriophage will destroy the bacteria, but the problem is, it'll destroy it before it can even use it. It doesn't want to destroy the bacteria before it can take advantage of it. The lysozyme needs to be made last because it basically kills the bacteria.

 

[2010premed]

Amazing clarification... thank you very much