Name: how viral genomes replicate
Uploaded: 2025-06-12T09:27:55.000Z
Duration: 1 min 26 s
Channel: JoVE

K12 Standards

Tennessee Academic Standards

High School

Biology

from-molecules-to-organisms-structures-and-processes

From Molecules to Organisms: Structures and Processes

BIO1.LS1.1

Size and Structure of Viral Genomes

I genomi virali variano per dimensioni, struttura e composizione. Sono costituiti da DNA o RNA, possono essere lineari o circolari ed esistono come molecole a singolo o doppio filamento. I virus a RNA tendono ad avere genomi più piccoli rispetto ai virus a DNA. L'RNA a senso positivo, come nel Poliovirus, agisce come un RNA messaggero. Mentre sia i virus a RNA a senso negativo che i virus a RNA a doppio filamento, si affidano all'RNA polimerasi RNA-dipendente per trascrivere i loro genomi in RNA a senso positivo prima della traduzione. I virus a DNA a singolo filamento, come i Parvovirus, formano un intermedio replicativo a doppio filamento. Il filamento di DNA a senso positivo condivide la stessa sequenza dell'mRNA, ma la trascrizione procede utilizzando il filamento complementare come stampo. Al contrario, il DNA a senso negativo deve prima formare un intermedio a doppio filamento. I virus a DNA a doppio filamento come gli Herpesvirus hanno tipicamente genomi più grandi e utilizzano l'ospite o le polimerasi virali per la replicazione. I retrovirus, come l'HIV, impiegano la trascrizione inversa per integrarsi nel genoma ospite, garantendo la persistenza a lungo termine.

dimensioni e struttura dei genomi virali

I genomi virali mostrano una straordinaria diversit&#224; in termini di dimensioni, struttura e composizione, elementi che influenzano le strategie replicative e le interazioni con le cellule ospiti. Questi genomi sono costituiti da DNA o RNA e possono presentarsi in forma lineare o circolare. Inoltre, possono essere a singolo filamento (ss) o a doppio filamento (ds), con ciascuna configurazione che incide sul modo in cui il virus si propaga all'interno dell'ospite. Gli RNA virus, ad esempio, possiedono generalmente genomi pi&#249; piccoli rispetto ai DNA virus, un fattore che contribuisce ai loro elevati tassi di mutazione e alla rapida evoluzione.
RNA Virus: Struttura e Funzione del Genoma
Gli RNA virus sono solitamente privi di meccanismi di correzione degli errori nelle loro polimerasi, il che comporta una maggiore frequenza di mutazioni e una rapida capacit&#224; di adattamento. Gli RNA virus a polarit&#224; positiva (plus-sense), come il Poliovirus, agiscono direttamente come RNA messaggero (mRNA), permettendo la traduzione immediata delle proteine virali una volta entrati nella cellula ospite. Al contrario, gli RNA virus a polarit&#224; negativa (minus-sense), come il virus della Rabbia, devono prima essere trascritti per produrre un mRNA complementare prima che possa avvenire la traduzione. Gli RNA virus a doppio filamento, come il Rotavirus, si affidano alla RNA polimerasi RNA-dipendente per trascrivere il loro genoma in mRNA, poich&#233; le cellule ospiti non possiedono enzimi in grado di elaborare direttamente l&#8217;RNA a doppio filamento.
DNA Virus: Strategie Replicative
A differenza degli RNA virus, i DNA virus adottano meccanismi replicativi distinti che assicurano la stabilit&#224; del genoma e, in alcuni casi, una persistenza prolungata nell&#8217;ospite. I virus a DNA a singolo filamento (ssDNA), come i Parvovirus, devono prima essere convertiti in un intermedio a doppio filamento prima della trascrizione. Analogamente, i virus a DNA a singolo filamento di polarit&#224; positiva richiedono la sintesi di un filamento complementare per creare un template funzionale a doppio filamento per l&#8217;espressione genica.
I virus a DNA a polarit&#224; negativa, come gli Epadnavirus, impiegano una strategia unica di trascrizione inversa. Invece di formare direttamente un intermedio a doppio filamento, questi virus sintetizzano un intermedio a RNA, che viene poi retrotrascritto nuovamente in DNA per la replicazione genomica.
Virus a DNA Doppio Filamento e Retrovirus
I virus a DNA a doppio filamento (dsDNA), come gli Herpesvirus, spesso possiedono genomi di grandi dimensioni e possono affidarsi alle polimerasi cellulari dell&#8217;ospite o codificare le proprie polimerasi per la replicazione del genoma. Questa capacit&#224; consente loro di instaurare infezioni latenti, persistendo nell&#8217;ospite per lunghi periodi e riattivandosi in condizioni favorevoli.
I retrovirus, come l&#8217;HIV, utilizzano la trascrittasi inversa per convertire il proprio genoma a RNA in DNA, che viene successivamente integrato nel genoma dell&#8217;ospite. Questa integrazione consente al virus di persistere all&#8217;interno delle cellule ospiti, restando in forma latente o replicandosi attivamente in funzione delle condizioni cellulari. Questa strategia facilita infezioni a lungo termine e l&#8217;evasione del sistema immunitario.

Dimensioni e Struttura dei Genomi Virali

I genomi virali mostrano una straordinaria diversit&#224; in termini di dimensioni, struttura e composizione, elementi che influenzano le strategie ...

Education

Didattica

JoVE Core

Microbiology

Microbiologia

Unit

Unità

Viruses

Virus

KEY TERMS AND CONCEPTS

TERMINI E CONCETTI CHIAVE

how viral genomes replicate

Viral genomes can be DNA or RNA, and their structure shapes how they replicate inside host cells. They may be linear or circular. They can also be single-stranded or double-stranded. These differences affect how a virus makes copies of itself and how it interacts with the host.

RNA viruses usually have smaller genomes than DNA viruses. That smaller size is linked to high mutation rates and fast evolution. RNA virus polymerases often lack proofreading, so mistakes are more common. This helps RNA viruses adapt quickly.

Plus-sense RNA viruses, such as Poliovirus, can act like messenger RNA, or mRNA. That means the host cell can translate them into viral proteins right away. Minus-sense RNA viruses, such as Rabies virus, must first be transcribed into complementary mRNA. Double-stranded RNA viruses, such as Rotavirus, also need RNA-dependent RNA polymerase to make mRNA because host cells do not have enzymes that can process double-stranded RNA directly.

DNA viruses use different replication strategies that often support more stable genomes. Single-stranded DNA viruses, such as Parvoviruses, must first become double-stranded before transcription can begin. Plus-strand DNA viruses also need a complementary strand to form a usable double-stranded template for gene expression. Minus-strand DNA viruses, such as Hepadnaviruses, use reverse transcription through an RNA intermediate before the genome is copied back into DNA.

Double-stranded DNA viruses, including Herpesviruses, often have larger genomes. They may rely on host-cell polymerases or encode their own polymerases for replication. This flexibility can help them establish latent infections, where the virus persists in the host for long periods and may reactivate later. Retroviruses, such as HIV, also use reverse transcriptase. They convert their RNA genome into DNA and integrate it into the host genome, which helps the virus persist in cells and can support either latent or active replication.

How Viral Genomes Replicate

introduction to virus

Virus Structure, Entry, and Replication

Viruses are biological entities that rely on host cells to make more copies of themselves. They do not have cells or their own metabolism, but they can show signs of life when they infect a host. Their basic structure includes a nucleic acid core, made of either DNA or RNA, surrounded by a protein coat called a capsid. Viruses are classified by the type of nucleic acid they contain and by their structure. Some viruses also have a lipid envelope that comes from the host cell membrane. Enveloped...

size and structure of viral genomes

Viral genomes can be DNA or RNA, and their structure shapes how they replicate inside host cells. They may be linear or circular. They can also be single-stranded or double-stranded. These differences affect how a virus makes copies of itself and how it interacts with the host. RNA viruses usually have smaller genomes than DNA viruses. That smaller size is linked to high mutation rates and fast evolution. RNA virus polymerases often lack proofreading, so mistakes are more common. This helps...

viral replication: lytic cycle

T4 Phage Infection of E. coli

T4 phage infection of E. coli follows a lytic cycle that lets the virus make many copies fast. Bacteriophages, or phages, are viruses that infect bacteria, and T-even phages such as T4 are known for this well-studied process. The cycle ends with the destruction of the bacterial host. The first step is attachment to the E. coli cell surface. Tail fibers on the phage bind to receptor molecules on the bacterial outer membrane, which helps the virus find the correct host. After binding, the...

viral replication: lysogenic cycle

Prophage Integration in Bacterial Cells

The lysogenic cycle shows how a bacteriophage can stay inside a bacterial cell without killing it right away. Temperate phages, such as bacteriophage lambda (λ), use this strategy to persist in Escherichia coli while the host cell remains alive. After attachment to the bacterial surface, the phage injects its genetic material into the cytoplasm. The linear phage genome then circularizes, which helps protect it from host nucleases. Next, phage-encoded integrase carries out recombination that...

dna bacteriophages

How DNA Phages Replicate in Bacteria

DNA bacteriophages are viruses that infect bacteria and use bacterial cell machinery to make more copies of themselves. They carry either single-stranded DNA (ssDNA) or double-stranded DNA (dsDNA), and each group uses a different replication strategy. Their life cycles also shape how they interact with hosts and how scientists use them in biotechnology and medicine. Some ssDNA phages keep their genomes very small and compact. The icosahedral phage ΦX174 shows this clearly because it uses...

viruses of archaea

Archaeal Virus Shapes and Extreme Survival

Archaeal viruses infect archaea that live in extreme places such as acidic hot springs and hydrothermal vents. These hosts often belong to the phyla Euryarchaeota and Crenarchaeota. The viruses help shape host evolution and gene transfer, which adds genetic diversity to microbial communities in harsh environments. Most archaeal viruses carry double-stranded DNA, or dsDNA, genomes. Some have single-stranded DNA, and some have RNA genomes. Their virions, or complete virus particles, show unusual...

viruses with rna genomes

RNA Virus Replication Strategies

RNA viruses use several replication strategies based on their genome type. They are grouped as positive-strand, negative-strand, or double-stranded RNA viruses. Some RNA viruses also use reverse transcription, which adds another layer to how they copy their genetic material. Positive-strand RNA viruses have genomes that can act like messenger RNA, or mRNA, as soon as they enter a cell. This lets the virus begin making proteins right away. Bacteriophage MS2 infects Escherichia coli by attaching...

the antiviral system of bacteria and archaea: crispr

the-antiviral-system-of-bacteria-and-archaea-crispr

How CRISPR Remembers Viral Infections

CRISPR is an adaptive immune system in bacteria and archaea that helps protect cells from viral infection. It works by identifying foreign genetic material, remembering it, and stopping the same invader later. In many cases, the main targets are bacteriophages, which are viruses that infect bacteria. The first defense step begins during an initial infection. Cas proteins, which are CRISPR-associated proteins, detect foreign DNA by looking for specific sequences called Protospacer Adjacent...

crispr/cas9 genome editing

CRISPR-Cas9 and DNA Repair in Cells

CRISPR-Cas9 uses a bacterial defense system to change DNA in cells. The CRISPR-Cas system first evolved in prokaryotes to protect bacteria from invading genetic material such as viruses and plasmids. Scientists later adapted it into a genome-editing tool for plants, animals, and humans. The key enzyme is Cas9, a DNA-cutting protein called an endonuclease from Streptococcus pyogenes. In the lab, a synthetic single guide RNA, or sgRNA, directs Cas9 to a chosen DNA site. The sgRNA matches the...

subviral agents

Viroids, Prions, and Satellite Viruses

Viroids, prions, and satellites are subviral agents that can cause infection even though they are not complete viruses. They resemble viruses in spread and disease, but each lacks one or more key viral parts, such as a capsid or the machinery needed for replication. Viroids are the simplest of these agents. They are circular, single-stranded RNA molecules with no protein coat. Viroids infect plants only and depend on host cell machinery to copy themselves. Host RNA polymerase replicates them...

key terms and concepts

Explore how RNA, DNA, and retroviral genomes replicate. Learn the roles of plus-sense, minus-sense, and double-stranded viruses in host cells.

How Viral Genomes Replicate | JoVE K12

JoVE Core Microbiology provides an engaging introduction to the microbial world and its influence on health, industry, and the environment. This comprehensive collection covers key concepts such as microbial structure, metabolism, genetics, and ecology. It introduces essential laboratory techniques and microscopy methods through visually engaging animations. Corresponding scientist-in-action videos bridge classroom concepts with real-world research and applications.

microbiology

Virginia  Standards of Learning

HIgh School

BIO.4

BIO.4.a

Alabama Course of Study Science

9-12

Unity and Diversity

9-12.B.4.13.a

Characteristics of Life

Biology is a natural science that studies life and living organisms, including their structure, function, development, interactions, evolution, ...

https://cloudfront.jove.com/files/media/science-education/science-education-thumbs/10647.jpg

Levels of Organization

Biological organization is the classification of biological structures, ranging from atoms at the bottom of the hierarchy to the Earth&#x27;s biosphere. ...

the-tree-of-life-bacteria-archaea-and-eukaryotes

The Tree of Life - Bacteria, Archaea, and Eukaryotes

Prokaryotic Cells

Prokaryotes are small unicellular organisms that include the domains &#8212; Archaea and Bacteria. Bacteria include many common microorganisms, such as ...

Introduction to Virus

Viruses are unique biological entities that blur the boundary between living and non-living systems. Although they lack cellular structure and metabolic ...

Viral genomes exhibit remarkable diversity in size, structure, and composition, influencing their replication strategies and interactions with host cells. ...

Compare and contrast existing models, identify patterns, and use structural and functional evidence to analyze the characteristics of life. Engage in argument about the designation of viruses as non-living based on these characteristics.
EXPLANATION: Students begin to develop patterns of living and non-living organisms in kindergarten and build on detailed characteristics of different classifications of living organisms throughout elementary and middle school. Biology 1 discussions introduce viral particles and viral cycles, building on student understanding of living organisms to engage in an argument regarding the classification of a viral particle as either living or non-living.

What are Cells?

Cells are the smallest and basic units of life, whether it is a single cell that forms the entire organism, e.g., in a bacterium, or trillions of them, ...

Eukaryotic Compartmentalization

One of the distinguishing features of eukaryotic cells is that they contain membrane-bound organelles, such as the nucleus and mitochondria, that carry ...

Eukaryotic Evolution

The endosymbiont theory is the most widely accepted theory of eukaryotic evolution; however, its progression is still somewhat debated. According to the ...

Animal and Plant Cell Structure

Animal and plant cells not only differ in their structure, function, and mode of nutrition but also in how they reproduce, specialize, and organize into ...

Evaluate comparative models of various cell types with a focus on organic molecules that make up cellular structures.
EXPLANATION: Students explicitly discuss the structure and function of major cellular organelles in seventh grade. Building on this understanding, Biology I students should shift their focus to the different types of cells found in organisms and how the role of each cell type relates to its composition and the prevalence of different organelles within that cell. An example might include the absence (or enucleation) of the nucleus in red blood cells in mammals providing for increased levels of oxygen transport in organisms or the lack of centrioles in most neurons. Varying cell types can include both prokaryotic and eukaryotic cell types.

BIO1.LS1.2

Nucleic Acids

Nucleic acids are the most important macromolecules for the continuity of life. They carry the cell&#39;s genetic blueprint and carry instructions for its ...

The DNA Helix

Deoxyribonucleic acid, or DNA, is the genetic material responsible for passing traits from generation to generation in all organisms and most viruses. DNA ...

DNA Base Pairing

Erwin Chargaff&#x2019;s rules on DNA equivalence paved the way for the discovery of base pairing in DNA. Chargaff&#x2019;s rules state that in a ...

The Central Dogma

The central dogma explains the flow of genetic information from DNA nucleotides to the amino acid sequence of proteins.
RNA is the Missing Link Between ...

DNA Packaging

Overview

Eukaryotes have large genomes compared to prokaryotes. In order to fit their genomes into a cell, eukaryotes must pack their DNA tightly inside ...

Organization of Genes

Overview

The genomes of eukaryotes can be structured in several functional categories. A strand of DNA is comprised of genes and intergenic regions. ...

Karyotyping

Describing the number and physical features of chromosomes can reveal abnormalities that underlie genetic diseases. This description is facilitated by ...

Replication in Prokaryotes

Overview

DNA replication has three main steps: initiation, elongation, and termination. Replication in prokaryotes begins when initiator proteins bind to ...

Replication in Eukaryotes

Overview

In eukaryotic cells, DNA replication is highly conserved and tightly regulated. Multiple linear chromosomes must be duplicated with high ...

Mutations

Overview

Mutations are changes in the sequence of DNA. These changes can occur spontaneously or they can be induced by exposure to environmental factors. ...

Transcription

Overview
Transcription is the process of synthesizing RNA from a DNA sequence by RNA polymerase. It is the first step in producing a protein from a gene ...

Translation

Lesson: Translation
Translation is the process of synthesizing proteins from the genetic information carried by messenger RNA (mRNA). Following ...

RNA Structure

Overview
The basic structure of RNA consists of a five-carbon sugar and one of four nitrogenous bases. Although most RNA is single-stranded, it can form ...

RNA Stability

Intact DNA strands can be found in fossils, while scientists sometimes struggle to keep RNA intact under laboratory conditions. The structural variations ...

pre-mRNA Processing

In eukaryotic cells, transcripts made by RNA polymerase are modified and processed before exiting the nucleus. Unprocessed RNA is called precursor mRNA or ...

Types of RNA

Overview
Three main types of RNA are involved in protein synthesis: messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA). These RNAs ...

MicroRNAs

siRNA - Small Interfering RNAs

Small interfering RNAs, or siRNAs, are short regulatory RNA molecules that can silence genes post-transcriptionally, as well as the transcriptional ...

piRNA - Piwi-interacting RNAs

PIWI-interacting RNAs, or piRNAs, are the most abundant short non-coding RNAs. More than 20,000 genes have been found in humans that code for piRNAs while ...

CRISPR and crRNAs

Bacteria and archaea are susceptible to viral infections just like eukaryotes; therefore, they have developed a unique adaptive immune system to protect ...

lncRNA - Long Non-coding RNAs

In humans, more than 80% of the genome gets transcribed. However, only around 2% of the genome codes for proteins. The remaining part produces non-coding ...

What are Proteins?

Protein Organization

Protein Folding

Protein Families

Protein families are groups of homologous proteins; that is, they have similarities in amino acid sequences and three-dimensional structures. Protein ...

conservation-of-protein-domains-over-different-proteins

Conservation of Protein Domains Over Different Proteins

Protein domains are small structurally independent units that are part of a single amino acid chain.&#160; Although these domains are often structurally ...

Globular and Fibrous Proteins

Many proteins can be classified into two distinct subtypes - globular or fibrous. These two types differ in their shapes and solubilities.
Globular ...

Intrinsically Disordered Proteins

Intrinsically disordered proteins are a group of proteins that do not fold into specific three-dimensional structures. Their structural flexibility allows ...

Protein Complex Assembly

Proteins can form homomeric complexes with another unit of the same protein or heteromeric complexes with different types.&#160; Most protein complexes ...

Conjugated Proteins

Simple proteins and protein complexes contain only amino acids. In contrast, many other proteins, called conjugated proteins, covalently bond with ...

Allosteric Proteins-ATCase

Binding sites linkages can regulate a protein&#39;s function.&#160; For example, enzyme activity is often regulated through a feedback mechanism where the ...

Amyloid Fibrils

Amyloid fibrils are aggregates of misfolded proteins.&#160; Under most circumstances, misfolded proteins are either refolded by chaperone proteins or ...

Cooperative Allosteric Transitions

Cooperative allosteric transitions can occur in multimeric proteins, where each subunit of the protein has its own ligand-binding site. When a ligand ...

Antibody Structure

Phosphorylation

Ligand Binding Sites

Proteins are dynamic macromolecules that carry out a wide variety of essential processes; however, the activities of most proteins depend on their ...

Protein Kinases and Phosphatases

Proteins undergo chemical modifications that trigger changes in the charge, structure, and conformation of the proteins. Phosphorylation, acetylation, ...

Protein-protein Interfaces

Many proteins form complexes to carry out their functions, making protein-protein interactions (PPIs) essential for an organism&#39;s survival. Most PPIs ...

GTPases and their Regulation

Guanine nucleotide-binding proteins (G-proteins), also known as GTPases, are a superfamily of proteins that regulate many cellular processes, such as cell ...

Conserved Binding Sites

Many proteins&#8217; biological role depends on their interactions with their ligands, small molecules that bind to specific locations on the protein ...

Covalently Linked Protein Regulators

Proteins can undergo many types of post-translational modifications, often in response to changes in their environment. These modifications play an ...

the-equilibrium-binding-constant-and-binding-strength

The Equilibrium Binding Constant and Binding Strength

The equilibrium binding constant (Kb) quantifies the strength of a protein-ligand interaction. Kb can be calculated as follows when the reaction is at ...

protein-complexes-with-interchangeable-parts

Protein Complexes with Interchangeable Parts

Groups of proteins may form a complex where each protein in this complex has a different role in the overall execution of the complex&#8217;s function. ...

Cofactors and Coenzymes

Mechanical Protein Functions

Proteins perform many mechanical functions in a cell. These proteins can be classified into two general categories- proteins that generate mechanical ...

Allosteric Regulation

Structural Protein Function

Structural proteins are a category of proteins responsible for functions ranging from cell shape and movement to providing support to major structures ...

Ligand Binding and Linkage

Allosteric proteins have more than one ligand binding site; the binding of a ligand to any of these sites influences the binding of ligands to the other ...

Protein Networks

An organism can have thousands of different proteins, and these proteins must cooperate to ensure the health of an organism. Proteins bind to other ...

Integrate evidence to develop a structural model of a DNA molecule. Using the model, develop and communicate an explanation for how DNA serves as a template for self-replication and encodes biological information.
EXPLANATION: Discussions of DNA in earlier grades have been limited to discussions of genes and the role of genes in the appearance and activities of an organism. Biology 1 represents a student's introduction to a molecular model of a DNA as well as the organization of DNA into genes and genes subsequently into chromosomes. Students should address interactions between genes in proteins which regulate both the shape and reproduction of DNA molecules. It is important to note that not all segments of DNA are transcribed for proteins. Portions of DNA are involved in regulating the expression of genes or affect the structure of the chromosomes (replication origin, centromeres, and telomeres).

BIO1.LS1.3

What is the Cell Cycle?

The cell cycle refers to the sequence of events occurring throughout a typical cell&#8217;s life. In eukaryotic cells, the somatic cell cycle has two ...

Interphase

The cell cycle occurs over approximately 24 hours (in a typical human cell) and in two distinct stages: interphase, which includes three phases of the ...

The Cell Cycle Control System

Positive Regulator Molecules

Inhibition of CDK Activity

S-Cdk Initiates DNA Replication

M-Cdk Drives Transition Into Mitosis

Mitogens and the Cell Cycle

Replicative Cell Senescence

Abnormal Proliferation

cells-coordinate-growth-and-proliferation

Cells Coordinate Growth and Proliferation

Create a model for the major events of the eukaryotic cell cycle, including mitosis. Compare and contrast the rates of cell division in various eukaryotic cell types in multicellular organisms.
EXPLANATION: Students first discuss mitosis in seventh grade, specifically focusing on the role of mitosis in creating genetically identical daughter cells. Biology 1 discussions should connect a student's understanding of gene expression and protein function with the process of mitosis to explore the differentiation of cell types from otherwise identical daughter cells. Discussions should also include varying rates of mitotic division and the relationship between these rates of division and the function of specific cell types within eukaryotic organisms. Examples may include the extremely limited use of mitosis by neurons due to their interconnectedness within neural networks or the rapid rates of mitosis with growing root tips.

BIO1.LS1.6

How Viral Genomes Replicate

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