Question

1. what are the main structural components of a virus? a) nucleus, ribosomes, and mitochondria b) capsid, genetic material, and sometimes an envelope c) cell wall, plasma membrane, and cytoplasm d) flagella, pili, and nucleus 2) which statement best describes the difference between the lytic and lysogenic cycles? a) the lytic cycle destroys the host cell, while the lysogenic cycle integrates viral dna without immediate destruction b) the lysogenic cycle kills the host cell, while the lytic cycle is harmless c) the lytic cycle allows the virus to replicate without entering the host cell d) both cycles occur at the same time in all viruses 3) how do retroviruses, such as hiv, differ from other viruses? a) they do not need a host cell to replicate b) they use reverse transcriptase to convert rna into dna c) they only infect bacteria d) they replicate using a double - stranded dna genome 4) which of the following is not a common way viruses are transmitted? a) direct contact with an infected person b) contaminated food and water c) exposure to radiation d) insect bites

Explanation:

1. Viruses are non - cellular entities. They have a protein coat called capsid, genetic material (DNA or RNA), and some have an outer envelope. Nucleus, ribosomes, mitochondria, cell wall, plasma membrane, etc. are components of cells, not viruses.
2. In the lytic cycle, the virus replicates and causes the lysis (destruction) of the host cell. In the lysogenic cycle, the viral DNA integrates into the host cell's DNA and replicates along with the host cell's DNA without immediate destruction.
3. Retroviruses like HIV have RNA as their genetic material and use reverse transcriptase to convert RNA into DNA during replication. All viruses need a host cell to replicate. Bacteriophages infect bacteria, not retroviruses.
4. Viruses are commonly transmitted through direct contact with an infected person, contaminated food and water, and insect bites. Exposure to radiation is not a common mode of virus transmission.

Answer:

1. B. Capsid, genetic material, and sometimes an envelope
2. A. The lytic cycle destroys the host cell, while the lysogenic cycle integrates viral DNA without immediate destruction
3. B. They use reverse transcriptase to convert RNA into DNA
4. C. Exposure to radiation