Virology: Virus Structure and Classification

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Questions and Answers

What is the primary focus of the morphological stage of microbiology development?

Study of microorganisms' morphological properties

Which of the following is NOT a component of bacterial taxonomy?

Isolation of microorganisms

What is the main characteristic of the modern stage of microbiology development?

Development of genetic engineering

What is the primary basis for the contemporary classification of microorganisms?

Phenotypic properties Signup and view all the answers

Who is credited with the discovery of viruses and their role in causing disease?

Ivanovsky Signup and view all the answers

What is the name of the system of classification of microorganisms that was widely accepted in 1974?

Bergey's classification Signup and view all the answers

What is the term for the naming of units in bacterial taxonomy?

Nomenclature Signup and view all the answers

What is the characteristic of a taxon in bacterial taxonomy?

A group of units regardless of hierarchic level Signup and view all the answers

What is the primary unit of heredity in an organism?

Gene Signup and view all the answers

What is the primary location of genes essential for bacterial growth?

Chromosome Signup and view all the answers

What is the characteristic of the infective agent of subviral agents?

It is a protein-free low molecular weight RNA Signup and view all the answers

What is the term for the collective structural and physiologic properties of a cell or an organism?

Phenotype Signup and view all the answers

What is the characteristic of bacterial cells?

They are haploid Signup and view all the answers

What is the molecular weight of the bacterial chromosome?

2x10^9 Signup and view all the answers

What is the primary function of the nucleic acid in a virion?

To carry genetic information and secure infectious properties Signup and view all the answers

Which of the following methods is used to determine the size of viruses?

All of the above Signup and view all the answers

What is the term for the symmetry of viruses that have a helical shape?

Helical Signup and view all the answers

Which of the following properties is NOT used in the classification of viruses?

Presence or absence of a cell wall Signup and view all the answers

Which of the following types of viruses has a single-stranded DNA genome?

Parvoviruses Signup and view all the answers

What carries genes associated with specialized functions in bacteria?

Plasmid Signup and view all the answers

What is the characteristic of extrachromosomal factors?

They are molecules of DNA with different molecular weights Signup and view all the answers

What is the term for the shape of viruses that have a spherical form, such as influenza and AIDS viruses?

Spherical Signup and view all the answers

What is the function of the supercapsid in a virus?

To serve as the principal antigen against which the host mounts its immune response Signup and view all the answers

Which of the following is a characteristic of enveloped viruses?

They are more sensitive to heat, detergents, and lipid solvents Signup and view all the answers

Study Notes

Virus Structure and Function

A supercapsid has the same functions as a capsid: adhesive and invasive, protective, and principal antigens against which the host mounts its immune response.
The presence of an envelope makes a virus more sensitive to heat, detergents, and lipid solvents.

Classification of Viruses

Based on the type of nucleic acid: DNA or RNA (but not both), number of strands, and polarity.
According to nucleocapsid symmetry: icosahedral or helical.
According to structure: presence or absence of a second membrane/supercapsid.
Viruses can be classified into three size groups: small (30-40 nm), middle (80-150 nm), and large (200-400 nm).
According to shape: spherical, rod-shaped, spermatozoid, bullet-shaped, star-shaped, or crown-shaped.

Microbial Genetics

The science of genetics defines and analyzes heredity, or constancy and change in physiologic functions.
The unit of heredity is the gene, a segment of DNA that carries information for a specific biochemical or physiologic property.
Genetic information is stored as a sequence of bases in DNA.
Prokaryotic genes are carried on the bacterial chromosome, a single circular DNA molecule.
Bacteria are haploid, having a single chromosome, in contrast to human cells, which are diploid.
Plasmids carry genes associated with specialized functions.

History of Microbiology

Ivanovsky showed that organisms passed through filters of small pore size and lacked a cellular structure.
This discovery led to the development of virology and immunology.
The stages of development of microbiology are:
- Morphological stage (XVII-XIX century)
- Physiological stage (XIX-XX century)
- Immunological and development of virology (XX century)
- Modern – molecular-genetic stage (XX-XXI century)

Morphology and Bacterial Taxonomy

Bacterial taxonomy comprises three components: classification, identification, and nomenclature.
Classification is based on phenotypic properties: morphological, physiological, and biochemical.
Morphology is characterized by shape and structure of microbial cell.
Physiological properties are characterized by growth on artificial nutrient media and character of growth on liquid media.
Biochemical properties are based on type of metabolism, fermentation of carbohydrates, and proteolytic activity.

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