1. Although generally not considered to be alive, a is studied alongside other microbes such as bacteria. 2. The protein coat that surrounds the nucleic acid of a virus is called a . 3. The is a viral life cycle that results in bursting of the host cell. 4. The is a viral life cycle in which the virus inserts its genome into the genome of its host, where it may remain dormant for long periods. 5. A is a viral genome that has inserted itself into the genome of its host. 6. A is a virus that specifically infects bacteria.

1. Virus is sometimes considere to be alive because of its ability to replicate. But, since the replication of the virus is immposible without the host, virus is more often called infectious agent (not organism). Virus can infect bacterial cells, human animal and plant cells. Their genetic material can be DNA or RNA, so the viruses are classified as DNA and RNA viruses. Beside genetic material, viral particles virions also contain protein coat and lipid envelope.

2.Virions (viral particles) contain genetic material (DNA or RNA), protein coat called capsid and lipid envelope. The role of capside is to provide protection to genetic material. It is composed of protomers-oligomer protein subunits. The structure of the capsid is helical or icosahedral. Capsid can be enveloped with lipid layer-viral envelope. Capsid is involved in the process of interaction with the host and with the delivery of the genome into the host.

3. The lytic lifestyle of the viruses (e.g. bacteriophage) can be described through the next steps:

attachment and injection into the host cell (e.g.bacterial cell)

synthesis of the early virus proteins which break down host's DNA

virus uses host's machinery (for the replication, transcription and translation) to produce the rest of its proteins and to form new virus particles.

host cell burst and many new virus particles are released.

After the destruction of the cell, the virus must find new host.

4. Lysogenic cycle is other type of viral life cycle. During the lysogenic cycle, virus does not kill the host immediate. It integrates its DNA into host's genome and stays dormant until conditions are optimal for reproduction. Viral genome replicates along with the host's. Dormant state lasts until host conditions deteriorate, then the prophage becomes active.

5. Prophage is a viral genome that is inserted into the genome of the host or sometimes it can existas an extrachromosomal plasmid. Bacteriophage integrates prophage during the lysogenic cycle (latent, dorman phase of the cycle). When the host conditions deteriorate, the prophage becomes active meaning it becomes excised from the host. This process is called prophage induction. The virus then begins with the lytic cycle.

6. Bacteriphage is a virus that infects the bacterial cell. Its structure is typical viral structure-genetic material (DNA or RNA), protein coat called capsid and lipid envelope. The lifecycle of bacteriophage includes the steps: attachment and penetration of the bacterial cell, synthesis of proteins and nucleic acid, assembly of virions, release of virions.

Bacteriophages are used as antibacterial agents (treatment of bacterial infections).