Explanation:

The measles virus has a negative-sense single-stranded RNA genome, which requires conversion into a positive-sense strand for protein synthesis.

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HIV spreads through unprotected sexual contact, contaminated needles, blood transfusions, and from mother to child during pregnancy or breastfeeding.

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HIV detection involves tests like antibody tests and nucleic acid tests (NATs) to confirm the presence of the virus in blood or saliva samples.

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ART involves a combination of drugs that target different stages of the HIV life cycle, such as inhibiting viral enzymes, to control the infection and slow disease progression.

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As HIV progresses to AIDS, the destruction of T lymphocytes weakens the immune system, leading to opportunistic infections such as tuberculosis, pneumonia, and certain cancers like Kaposi's sarcoma.

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In the asymptomatic stage, which can last up to ten years, the virus continues replicating and weakening the immune system, even though no symptoms are evident.

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HIV hijacks the host cell’s ribosomes to translate viral mRNA into proteins necessary for assembling new viral particles, parasitizing the host cell's machinery.

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During the budding stage, new HIV particles are released from the host cell by pinching off from the cell membrane, taking part of the host’s lipid bilayer as their envelope.

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By destroying Helper T cells, HIV weakens the immune system's ability to coordinate responses, such as activating B cells for antibody production and cytotoxic T cells to eliminate infected cells.

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The glycoprotein gp120 on HIV acts like a "lock and key," binding specifically to CD4 receptors on Helper T cells, which enables the virus to enter and infect these cells.

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HIV uses gp120 glycoproteins on its surface to bind to CD4 receptors and co-receptors on host Helper T cells, initiating cell entry through endocytosis.

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HIV speciically targets CD+ Helper T lymphocytes, which are crucial for coordinating the immune response by activating other immune cells like cytotoxic T cells and B cells.

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During transcription, the integrated viral DNA produces mRNA, which is translated into viral proteins necessary for the assembly of new viruses.

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HIV integrates its DNA into the host genome, where it can remain inactive for years, avoiding immune detection and reactivating under specific conditions.

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In the budding step, newly formed HIV particles are released from the host cell, acquiring a lipid envelope from the host cell membrane in the process.

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During integration, the viral DNA synthesized by reverse transcriptase is inserted into the host's DNA using the enzyme integrase, allowing the virus to use the host machinery for replication.

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HIV uses glycoproteins gp120 and gp41 to bind to CD4 receptors and co-receptors on host lymphocyte cells, facilitating virus entry.

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Reverse transcriptase is an enzyme in HIV that converts its RNA genome into DNA, enabling integration into the host cell’s DNA for replication.

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HIV contains two single-stranded RNA molecules as its genetic material, which are enclosed in a protein capsid and surrounded by a lipid envelope.

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The helical capsid of TMV completes about 130 turns per rod, creating its characteristic rod-like structure.

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Each capsomere of TMV contains approximately 158 amino acids, which contribute to the structure and functionality of the viral capsid.

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TMV has a helical arrangement of capsomeres, which spiral around the RNA genome to form a rod-like structure.

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The capsid is the protein coat of TMV that protects its RNA genome. It is composed of numerous protein subunits called capsomeres.

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TMV is an RNA virus with a centrally located single-stranded RNA genome that serves as its genetic material, surrounded by a protein coat.

Explanation:

Tail fibers recognize and bind to specific receptor sites on the bacterial surface, ensuring the bacteriophage attaches only to compatible host cells.

Explanation:
The base plate has proteinaceous retractable pins that pierce the bacterial cell wall, creating a path for the viral DNA to enter the host cell.

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The tail sheath contracts during infection, driving the tail tube through the bacterial cell wall and allowing the phage DNA to enter the host cytoplasm

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Tail fibers extend from the base plate and play a critical role in identifying and attaching to specific receptor sites on the bacterial surface.

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The base plate, located at the end of the tail, contains tail fibers that bind to specific receptors on the host cell, ensuring stable attachment for DNA injection.

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The tail of a bacteriophage connects the head to the host cell and functions as a tube-like structure that facilitates the transfer of DNA into the host.

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The head of a bacteriophage is polyhedral (icosahedral) and contains double-stranded DNA, which carries the genetic instructions for virus replication.

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RNA is chemically less stable than DNA, making RNA viruses more susceptible to damage under extreme environmental conditions, such as high temperatures or UV exposure.

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Lipid-enveloped viruses, such as influenza, are more sensitive to changes in relative humidity compared to non-lipid-enveloped viruses, as their lipid layer is prone to environmental degradation.

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Airborne viruses use expelled organic material, such as saliva or mucous, to shield themselves from environmental conditions, such as dryness or heat, during coughing or sneezing.

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A temperature of 60°C or higher is usually sufficient to inactivate most viruses by damaging their nucleic acids or proteins.

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High temperatures can denature viral proteins and dissociate capsids, inactivating viruses. DNA viruses are generally more resistant than RNA viruses to such damage.

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Viruses can survive outside a host under favorable environmental conditions such as specific temperature and pH, maintaining their infectivity until they find a host.

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Viruses frequently mutate and alter their genome to evade host immune responses, making treatments like vaccines less effective over time.

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Viruses are obligate intracellular parasites, meaning they require a living host cell to provide the machinery and energy for replication and protein synthesis.

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Viruses contain nucleic acids (either DNA or RNA) as their genetic material. These nucleic acids direct the host cell to replicate the viral genome and produce new viral particles.

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Viruses use the host cell's enzymes, organelles, and metabolic machinery to replicate their genome and produce proteins, as they lack the ability to do so on their own.

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Viruses depend on host cells to replicate and produce proteins, as they lack the necessary machinery to carry out these processes independently. The host provides all vital functions required for the virus's survival.

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Viruses are noncellular because they lack organelles, metabolic machinery, and the ability to generate energy or synthesize proteins independently. They require a host cell for replication and survival.

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Reverse-transcribing viruses have a unique replication mechanism where their RNA genome is transcribed into DNA for integration into the host genome. Examples include HIV and Hepatitis B.

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Single-stranded RNA viruses with a DNA intermediate, like HIV, use reverse transcriptase to form DNA, which is integrated into the host genome for further transcription and translation.

Explanation:

Hepatitis B virus has a double-stranded DNA genome and replicates using an RNA intermediate. It employs reverse transcription to replicate its genome.

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Single-stranded RNA viruses with a DNA intermediate, such as retroviruses like HIV, have a positive-sense RNA genome. They convert RNA into DNA for integration into the host genome during replication.

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Reverse-transcribing viruses, such as HIV, use the enzyme reverse transcriptase to convert their RNA genome into DNA, which integrates into the host genome for replication.

Explanation:

Negative-sense RNA viruses, like Rhabdoviruses and Paramyxoviruses, must synthesize a complementary mRNA strand from their RNA genome using host cell enzymes before translation can occur.

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Reoviruses are double-stranded RNA viruses, while Dengue virus, Hepatitis C virus, and Coronaviruses are examples of positive-sense single-stranded RNA viruses.

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In double-stranded RNA viruses, the mRNA is used for translating viral proteins and replicating the genome for producing new progeny.

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Double-stranded RNA viruses use host cell enzymes to synthesize single-stranded mRNA, which serves as a template for protein synthesis and viral replication.

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Positive-sense RNA viruses have genomes that are directly translated by the host's ribosomes into proteins without requiring any intermediate steps.

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Positive-sense single-stranded RNA viruses, such as Coronaviruses, Dengue virus, and Hepatitis C virus, have RNA genomes that function directly as mRNA, allowing immediate translation in host cells.

Explanation:

Double-stranded RNA viruses have a genome made of two RNA strands. They use host cell enzymes to produce single-stranded mRNA for protein synthesis and replication. An example is Reoviruses.

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David Baltimore classified viruses into groups based on their genome type (DNA or RNA, single-stranded or double-stranded) and their replication mechanisms.

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Double-stranded RNA viruses use one strand of their RNA genome as a template to synthesize mRNA, which is then used for translation and replication.

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Double-stranded RNA viruses, like Reoviruses, use their genome to produce single-stranded mRNA, which is translated into proteins and replicated within host cells.

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Single-stranded DNA viruses must become double-stranded in the host cell before synthesizing mRNA to produce viral proteins and replicate.

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Single-stranded DNA viruses, such as Parvoviruses, convert their single-stranded DNA to double-stranded DNA in host cells to synthesize mRNA.

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Flu viruses have an enveloped capsid, where a lipid membrane surrounds the protein capsid, aiding in host cell infection.

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Tobacco Mosaic Virus (TMV) has a helical capsid, where the capsomeres are arranged in a spiral, giving it a rod-like shape.

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Plant viruses, such as TMV, generally have RNA genomes. These viruses infect plants and are usually rod-shaped.

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T4 phages are bacteriophages, viruses that infect bacteria. They have a head-and-tail structure and use double-stranded DNA as their genetic material.

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Zoophages, or animal viruses, often have spherical shapes. Examples include Rhinoviruses (common cold) and Covid-19, which infect animals or humans.

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Influenza viruses are spherical in shape, with an envelope containing glycoprotein spikes that help them attach to host cells.

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Glycoprotein spikes on the viral envelope help the virus identify and attach to specific host cells, facilitating the process of infection.

Explanation:

Helical viruses have capsids arranged in a spiral or helical pattern, forming a rod-like shape. Examples include the Tobacco Mosaic Virus (TMV).

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Tadpole-shaped viruses, like bacteriophages, have a distinct head and tail structure that allows them to infect bacterial cells by injecting their genetic material.

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Polyhedral viruses have a capsid with 20 triangular faces, forming a symmetrical structure. This is a common shape for many viruses, such as adenoviruses.

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The inner core of a virus contains its genome, which can be DNA or RNA, single-stranded (ss) or double-stranded (ds). This genetic material carries instructions for virus replication.

Explanation:

In an icosahedral capsid, capsomeres are arranged to form a polyhedron with 20 triangular faces, creating a symmetrical and spherical structure

Explanation:

Some viruses have an outer lipoprotein layer called an envelope, which surrounds the capsid and helps in infecting host cells. The envelope is derived from the host cell membrane.

Explanation:

When capsomeres are arranged helically, they form a hollow coil, giving the virus a rod-like appearance, as seen in viruses like the Tobacco Mosaic Virus (TMV).

Explanation:

Capsomeres are identical protein subunits that assemble to form the capsid. Their arrangement and number are specific to the type of virus.

Explanation:

The capsid is the protein coat of a virus, made up of smaller protein units called capsomeres. It protects the viral genetic material and helps the virus attach to host cells.

Explanation:

Respiration is a metabolic activity that viruses cannot perform because they lack cellular organelles. This makes it a non-living characteristic of viruses.

Explanation:

viruses lack cellular organelles, which are necessary for performing metabolic activities like respiration and energy production.

Explanation:

Viruses exhibit non-living characteristics like the ability to remain inactive for indefinite periods and crystallize outside the host.

Explanation:

Viruses cannot replicate or perform any life processes outside a host cell, making them intracellular obligate parasites.

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Viruses contain either DNA or RNA as their genetic material, which determines their functionality and ability to mutate.

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Viruses are described as replicating like living organisms by utilizing host cellular contents, as they lack the machinery for independent replication.

Explanation:

Viruses are a significant threat to human health and the economy, causing diseases like smallpox, influenza, and COVID-19, as well as crop and livestock damage.

Explanation:

Living things categorizes into two groups: living entities or molecules (like DNA and proteins) and complete cell-based organisms.