Name: how viruses swap genes and spread
Uploaded: 2019-03-11T09:21:24.000Z
Duration: 57 s
Channel: JoVE

K12 Standards

Louisiana Student Standards for Science

High School

Life Sciences

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

From Molecules To Organisms: Structures And Processes

HS-LS1-8

Viral Recombination

- [Istruttore] Alcune cellule
possono essere infettate

contemporaneamente da due
diversi ceppi di un virus,

causando un mix di entrambe
le sequenze genetiche

in un processo chiamato
ricombinazione virale.

Più specificamente, dopo
che il virus è entrato

nel citoplasma della
cellula, si disassemblano

e iniziano a replicare i loro genomi.

Regioni simili di ciascun
genoma possono accoppiarsi

e scambiare pezzi, ricollegando i fili.

Oppure, i virus possono scambiare
alcuni dei loro segmenti

in un processo chiamato
riassortimento, in cui i nuovi virus

prodotti all'interno della
cellula hanno un mix di ceppi,

come metà dei loro segmenti da un ceppo

e l'altra metà dal ceppo due.

Questi virus appena
formati si sono ora evoluti

dai due virus originali,
formando popolazioni

che potrebbero continuare
a cambiare nel tempo.

He, Ping, Guojun Wang, Yanning Mo, Qingxiong Yu, Xiong Xiao, Wenjuan Yang, Weifeng Zhao, et al. "Nuovi virus influenzali a triplo riassortimento nei maiali, Guangxi, Cina". Microbi emergenti e infezioni 7 (16 maggio 2018). <a href="https://doi.org/10.1038/s41426-018-0088-z" target="__blank">https://doi.org/10.1038/s41426-018-0088-z</a>.

ricombinazione dei virus

Le cellule sono talvolta infettate da più di un virus contemporaneamente. Quando due virus si smontano per esporre i loro genomi per la replicazione nella stessa cellula, regioni simili dei loro genomi possono accoppiarsi e scambiare sequenze in un processo chiamato ricombinazione. In alternativa, i virus con genomi segmentati possono scambiare segmenti in un processo chiamato riassortimento.

<h4>La ricombinazione virale può creare nuove malattie</h4>

Alcune malattie possono infettare più specie. Ad esempio, i suini possono essere infettati da alcuni virus umani e uccelli, oltre ai virus che di solito infettano i maiali. Poiché i virus possono ricombinarsi quando coinfettano la stessa cellula, i maiali possono agire come "vasi di miscelazione" che ricombinano i virus di altre specie per creare nuovi virus che a volte possono infettare gli esseri umani. Questo fenomeno preoccupante rappresenta un percorso attraverso il quale il materiale infettivo di altre specie può entrare nella popolazione umana. Le malattie che si spostano dagli animali agli esseri umani sono conosciute come zoonosi. Gli esseri umani possono essere altamente suscettibili a tali virus perché non abbiamo alcuna storia di esposizione che avrebbe generato l'immunità.

L'influenza A è un primo esempio della teoria del "vaso di miscelazione" della malattia virale. La ricerca ha dimostrato che i virus dell'influenza umana, che si sono riproposti all'interno degli ospiti dei maiali. Questi eventi hanno prodotto virus "doppio reassortante" che contenevano geni provenienti da virus umani e avidi e virus "triplo-reassortante" che contenevano geni provenienti da virus umani, uccelli e suini. Nei Paesi Bassi, un virus reassortante composto da geni dell'influenza umana e aviaria è stato trasmesso dai suini all'uomo.

Ricombinazione dei virus

Cells are sometimes infected by more than one virus at once. When two viruses disassemble to expose their genomes for replication in the same cell, ...

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how viruses swap genes and spread

Viral gene swapping can happen when more than one virus infects the same cell. After the viruses break open and expose their genomes for replication, matching regions can pair up and exchange sequences. This process is called recombination. Viruses with segmented genomes can also swap whole segments, which is called reassortment.

These changes can help create new diseases. Some diseases can infect more than one species. Pigs can be infected by some human and bird viruses, along with the viruses that usually infect pigs. When different viruses co-infect the same pig cell, the pig can act as a mixing vessel and help produce new viruses that may infect humans.

This matters because diseases that move from animals to humans are called zoonoses. Humans can be highly susceptible to these viruses because we may not have previous exposure. Without that exposure, we would not have developed immunity. Influenza A is a clear example of the mixing vessel theory. Research has shown that pig, bird, and human influenza A viruses have reassorted inside pig hosts.

Some of those events produced double reassortant viruses with genes from human and bird viruses. Others produced triple-reassortant viruses with genes from human, bird, and pig viruses. In the Netherlands, a reassortant virus made from human and bird flu genes was passed from pigs to humans.

How Viruses Swap Genes and Spread

what are viruses?

How Viruses Infect Cells and Multiply

Viruses infect cells and make new copies by using a host cell’s own machinery. A virus is a tiny infectious particle with an RNA or DNA genome inside a protective protein coat. It cannot reproduce on its own, so it must enter a cell to make more viruses. After infection, the virus sheds its protein coat and uses the host cell to transcribe and translate its genetic material. The cell then assembles many new viral particles. In many cases, these new viruses rupture the host cell and kill it.

viral structure

How Virus Shapes Help Infection

Viruses have specific structures that help them infect host cells and trigger immune responses. Each virus has a core that contains either a DNA-based or RNA-based genome. That core is surrounded by a protective protein coat called the capsid. The capsid is made of smaller subunits called capsomeres. The capsid and the genome-containing core together are called the nucleocapsid. Viruses are often grouped by capsid design. Most viruses have either icosahedral or helical capsids, but some have...

lytic cycle of bacteriophages

How Phages Infect and Burst Bacteria

Bacteriophages, or phages, are viruses that infect bacteria. They have a distinctive head-tail shape. In the lytic cycle, a phage first attaches to the outside of a bacterial cell. Tail proteins bind to specific receptor proteins on the bacterium’s surface. After attachment, the phage tail injects its DNA genome into the bacterial cytoplasm. The phage then uses the bacterium’s cellular machinery to make proteins needed for replication and dispersal. When phage replication is complete, some of...

lysogenic cycle of bacteriophages

Prophage Integration in Bacteria

The lysogenic cycle shows how bacteriophages can infect bacteria without killing the host right away. In this cycle, the phage genome joins the bacterial genome. The integrated phage DNA is called a prophage, and the bacterium copies it each time it replicates. Some prophages can switch back into the lytic cycle. This change can happen after DNA damage or even without an obvious outside trigger. When the prophage is induced, the phage begins making new virus particles again. Prophages can...

retrovirus life cycles

How Retroviruses Replicate in Host Cells

Retroviruses replicate by copying their RNA genome into DNA inside a host cell. After entry, the viral enzyme reverse transcriptase makes a double-stranded DNA copy from the single-stranded RNA genome. The viral DNA is then carried into the nucleus and inserted into the host genome by integrase. Once integrated, the retroviral DNA is transcribed whenever the host genome is transcribed. This produces new viral RNA that can be copied and used again. The new RNA moves into the cytoplasm, where it...

viral recombination

Viral gene swapping can happen when more than one virus infects the same cell. After the viruses break open and expose their genomes for replication, matching regions can pair up and exchange sequences. This process is called recombination. Viruses with segmented genomes can also swap whole segments, which is called reassortment. These changes can help create new diseases. Some diseases can infect more than one species. Pigs can be infected by some human and bird viruses, along with the...

viral mutations

How Virus Mutations Drive Outbreaks

Virus mutations can change how quickly a virus evolves and spreads. A mutation is a change in the sequence of bases in DNA or RNA. Some mutations happen when the genome is copied. They are caused by errors made by polymerase enzymes, which replicate DNA or RNA. RNA viruses often change faster than DNA viruses because RNA polymerase does not proofread its work. That means RNA-based genomes, such as HIV, can gather mutations more quickly. Mutation and recombination give viruses the raw material...

key terms and concepts

Learn how viral recombination and reassortment happen when viruses infect the same cell, and how pigs can help new flu viruses spread to humans.

How Viruses Swap Genes and Spread | JoVE K12

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What is Gene Expression?

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Transcription

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HS-LS1-1

Characteristics of Life

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Phylogeny

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HS-LS1-2

Overview of Metabolism

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Regulation of Metabolism

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Positive and Negative Feedback Loops

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Negative and Positive Feedback

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HS-LS1-3

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Chromosome Duplication

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HS-LS1-4

How Viruses Swap Genes and Spread

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