While viral genome sizes vary significantly, some of the smallest viruses, such as certain bacteriophages or small animal viruses, contain a minimal set of genes, often cited as approximately four, required for replication and capsid formation.
2282
How many lipid layers typically compose the envelope of a viral particle?
The viral envelope is derived from host cell membranes and typically consists of a lipid bilayer. This bilayer structure is essential for the virus to fuse with host cell membranes during the infection process.
2283
Which component is typically found within the liquid suspension of viral protein molecules?
In many viral studies, particularly those involving RNA viruses, the viral RNA is found associated with the protein capsid. The question likely refers to the genetic material contained within the proteinaceous structure of the virion.
2284
What term describes retroviruses that contain two identical strands of RNA within their genome?
Retroviruses, such as HIV, are considered diploid because they carry two identical copies of their single-stranded RNA genome. This diploid nature is significant for genetic recombination during the reverse transcription process.
2285
Which term identifies a virus that lacks a lipid envelope?
In older viral classification systems, 'haplovirales' was used to categorize viruses that do not possess an outer lipid envelope, often referred to as naked viruses. These viruses rely solely on their protein capsid for structural integrity.
2286
Which term describes a virus with a binal symmetry containing DNA?
In the historical classification of viruses based on symmetry and nucleic acid content, 'deoxybinala' refers to viruses that possess DNA and exhibit binal symmetry, meaning they have both icosahedral and helical components, such as T-even bacteriophages.
2287
Which viral structure is primarily responsible for the attachment of a virion to a host cell?
The capsid, or the protein coat of the virus, contains specific proteins or glycoproteins that act as ligands. These ligands bind to specific receptors on the surface of the host cell, facilitating the entry of the virus.
2288
In viral replication, what is the functional role of a positive-sense (+) RNA strand?
A positive-sense (+) RNA strand is equivalent to messenger RNA (mRNA). It can be directly translated by the host cell's ribosomes into viral proteins immediately upon entering the host cell, without needing prior transcription.
2289
Which morphological form of Streptococcus pneumoniae is characterized as non-virulent and mutant?
The rough (R) form of Streptococcus pneumoniae lacks the polysaccharide capsule required for virulence. Because it cannot evade the host immune system, it is considered non-virulent. This phenotype is often associated with mutations that prevent the synthesis of the protective capsule.
2290
What is the term for the genetic recombination process where a bacterium actively takes up naked DNA from its environment?
Transformation is a mechanism of horizontal gene transfer in bacteria where a competent cell takes up free, naked DNA fragments from the surrounding medium. Once inside, the DNA may be integrated into the bacterial chromosome, potentially altering the genetic makeup of the recipient cell.
