Question

How is the classification system of viruses described? Which of the following demonstrates the classification system?

A) Viruses classified by shape and color
B) Viruses classified by their impact on the human body
C) Viruses classified by the type of genetic material and replication method
D) Viruses classified by the host organism they infect

Answer 1

Viruses are classified based on physical and biochemical properties such as capsid shape, nucleic acid type, replication method, host organism, and disease type. The correct demonstration of the classification system is C) Viruses classified by the type of genetic material and replication method. This aligns with the commonly used Baltimore classification scheme and the ICTV guidelines.

Step-by-step explanation:

Classification of Viruses

The classification system of viruses is based mainly on physical and biochemical characteristics of viral particles. These include the capsid shape, the type of nucleic acid (DNA or RNA, whether it is double-stranded (ds) or single-stranded (ss)), the mechanism of replication, their host organisms, and sometimes the type of disease they cause.

Answering the student's question, the statement that demonstrates the classification system is C) Viruses classified by the type of genetic material and replication method. This is consistent with the Baltimore classification scheme, which is the most commonly used method today and primarily classifies viruses based on how messenger RNA (mRNA) is produced during their replication cycles.

Viruses are further classified by the International Committee on Taxonomy of Viruses (ICTV), which uses genetic similarity to group viruses. The ICTV classification categorizes viruses into orders, families, and genera. However, because of the extensive diversity and evolving nature of viruses, the virus classification system is subject to constant updates and revisions.

Answer 2

Viruses are classified based on nucleic acid type, replication method, capsid shape, and the presence of an envelope, among other factors. The Baltimore classification system is widely used and categorizes viruses by their mRNA synthesis methods. The ICTV provides a formal genetic-similarity-based classification. Option C) Viruses classified by the type of genetic material and replication method is the correct answer.

Step-by-step explanation:

Classification of Viruses

The classification system of viruses is complex due to their unique nature, which doesn't fit neatly into the biological classification system of cellular organisms. Viruses are primarily classified based on the type of nucleic acid they contain (DNA or RNA), capsid shape, presence or absence of an envelope, method of replication, and their host range.

The most widely recognized system is the Baltimore classification scheme, which categorizes viruses by their mechanism of messenger RNA (mRNA) production. This system encompasses seven main groups differing in their strategies for synthesizing mRNA.

Another important aspect is the structure of the viral capsid and whether the virus is enveloped or not. These physical characteristics, along with the type of genetic material (double-stranded or single-stranded, linear or circular, segmented or non-segmented), provide key details for classification.

Furthermore, viruses can be informally grouped based on shared characteristics such as morphology, chemistry, capsid shape, and specific genes or enzymes they may possess. Examples of such informal groupings include herpesviruses as dsDNA enveloped viruses, human immunodeficiency virus (HIV) as a +ssRNA enveloped virus, and tobacco mosaic virus as a +ssRNA virus.

The International Committee on Taxonomy of Viruses (ICTV) offers a more formal and genetic similarity-based classification system. This puts viruses into orders, families, genera, and species, with a significant number of groups remaining unassigned due to the constant discovery and evaluation of new viral types. Ongoing research often refines virus classification, and the ICTV website provides updated classifications.