What are the genetic and structural characteristics that define a polymorphic virus?4 answersPolymorphic viruses exhibit genetic and structural variability. Genetically, they employ obfuscation techniques like encryption, decryption engines, and code transformation to hinder analysis. Structurally, polymorphic viruses can manifest diverse architectures due to minor changes in conditions or protein sequences, leading to the emergence of different forms from the same native system. In the case of human T-cell leukemia virus type 1 (HTLV-1), cryo-transmission electron microscopy revealed polymorphic virus particles with varying capsid core morphologies, impacting infectivity. These characteristics highlight the adaptability and complexity of polymorphic viruses, posing challenges for detection and analysis in the realm of cybersecurity and virology.
What is the structure of a virus?4 answersViruses have a protein coat called a capsid that protects their genetic material. The capsid can be either enveloped or nonenveloped, depending on the presence of a lipid membrane surrounding it. The capsid structure can be either helical or icosahedral. Helical capsids are built by numerous building blocks, while icosahedral capsids have 20 sides, each composed of an equilateral triangle. The capsids are made up of repeated contacts between protein subunits, which give them stability. The viral capsid functions to protect the genetic material from physical and chemical damage. Some viruses also have an outer lipid envelope in which viral proteins are embedded. The structure of viruses is diverse, with different shapes and sizes, but they all have a capsid that plays a crucial role in protecting their genetic material.
How is a viral isolate defined?5 answersA viral isolate is not defined by a specific genomic sequence, but rather by a population structure consisting of a collection of related mutants or sequences. This population structure, known as viral quasispecies, is characterized by the presence of multiple related sequences within a viral population. The concept of quasispecies has been confirmed by cloning-sequencing techniques and deep sequencing methodologies. The viral quasispecies dynamics explain the adaptive potential of viruses, including their response to antiviral treatments.
What is the structure of the Rift Valley fever virus genome?5 answersThe structure of the Rift Valley fever virus (RVFV) genome consists of three segments: small (S), medium (M), and large (L). The S segment encodes the nucleocapsid protein, the M segment encodes the glycoproteins Gn and Gc, and the L segment encodes the RNA-dependent RNA polymerase (RdRp). The RdRp is a multifunctional enzyme responsible for viral replication and transcription. The genome segments replicate near the site of infection before spreading throughout the cytoplasm and translocating to the virion assembly site at the Golgi network. The intracellular ratio of S, M, and L genome segments approaches 1:1:1, but major differences in segment ratios can be observed among cells. The copackaging of the different segments into a single virion is a non-selective process, and the majority of virions lack one or more genome segments.
What are the different theories of viral origin?5 answersViruses have different proposed theories for their origin. One theory suggests that viruses descended from primitive precellular life forms, while another theory proposes that viruses are escaped cellular genetic elements. A third theory suggests that viruses devolved from more complex intracellular parasites. However, none of these theories can explain the origins of all viruses, and it is widely accepted that distinct lineages of viruses evolved through different mechanisms. Another theory, known as the chimeric scenario, suggests that different types of primordial replicons gave rise to viruses by recruiting host proteins for virion formation. Additionally, it is believed that new groups of viruses have repeatedly emerged throughout the evolution of life, often displacing ancestral genes. These theories provide different perspectives on the origins of viruses and highlight the complexity of their evolutionary history.
What are the similarities and differences between viruses and viroids?5 answersViruses and viroids are both biological entities that can cause diseases. However, there are several differences between them. Viruses are cellular entities that contain genetic material enclosed in a protein coat. They can infect a wide range of hosts, including humans, animals, and plants. In contrast, viroids are acellular entities that consist of single-stranded RNA molecules without a protein coat. They are smaller in size compared to viruses and are known to infect only plants. Another difference is that viruses have the ability to encode proteins, while viroids do not. Despite these differences, there are also some similarities between viruses and viroids. Both can replicate within their host cells and cause diseases. Additionally, recent studies have suggested that viroids and some viruses share common replication features, indicating a possible evolutionary relationship between them.