Name: how viruses infect cells and multiply
Uploaded: 2019-03-11T09:21:23.000Z
Duration: 50 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

What are Viruses?

- [Anlatıcı] Virüs, konak bir hücreyi ele geçirip onun içinde çoğalmak için kendi genomik malzemesini RNA ya da DNA şeklinde taşıyan bir yapıdır.
 Virüs konak hücrenin yüzey reseptörlerine bağlanınca, içine girer ve hızla parçalanarak genetik malzemesini yayar.
 DNA virüslerinde, viral DNA, konak hücrenin kopyalama proteinlerini, viral genomun yeni kopyalarını sentezlemek için yönlendirir.
Bunlar daha sonra viral proteinler olarak kopyalanır.
 Son olarak konak, bu viral bileşenleri bir araya getirip yeni nesiller oluşturur, tek bir virüs tanesinin binlercesini üretmesine izin vererek çoğunlukla konak hücrenin ölümüne neden olur.

Yamauchi, Yohei ve Ari Helenius. "Bir Bakışta Virüs Girişi." J Cell Sci 126, no. 6 (15 Mart 2013): 1289–95. [<a href="https://doi.org/10.1242/jcs.119685" target="__blank">Kaynak</a>]

Lin, Derek M, Britt Koskella ve Henry C Lin. "Faj Tedavisi: Çoklu İlaç Direnci Çağında Antibiyotiklere Bir Alternatif." Dünya Gastrointestinal Farmakoloji ve Terapötik Dergisi 8, no. 3 (6 Ağustos 2017): 162–73. [<a href="https://doi.org/10.4292/wjgpt.v8.i3.162" target="__blank">Kaynak</a>]

Nicaise, Valérie. "Virüslere Karşı Mahsul Bağışıklığı: Sonuçlar ve Gelecekteki Zorluklar." Bitki Biliminde Sınırlar 5 (21 Kasım 2014). [<a href="https://doi.org/10.3389/fpls.2014.00660" target="__blank">Kaynak</a>]

virüsler nelerdir?

<h4>Genel bakış</h4>

Virüs, bir protein kabuğunun içinde bulunan bir RNA veya DNA genomundan oluşan mikroskobik enfeksiyöz bir parçacıktır. Kendi kendine üreyemez: sadece bir hücreye girerek ve hücresel makinelerini kullanarak daha fazla virüs üretebilir. Bir virüs bir konak hücreye bulaştığında, protein kılıfını çıkarır ve konakçının mekanizmalarını kullanarak genetik materyalini çoğaltır. Enfekte hücre içinde çoğaltılan bileşenler binlerce viral soya dönüştürülür ve bu da ev sahibi hücreyi parçalayıp öldürebilir. Yeni virüsler daha sonra daha fazla konak hücreleri enfekte eder.

<h4>Neden Virüsler Çalışılır?</h4>

Virüsler farklı türde hücrelere bulaşabilir: bakteriler, bitkiler ve hayvanlar. Bakteriyofaj (veya fajlar) adı verilen bakterileri hedef alan virüsler çok boldur. Mevcut araştırmalarda insanlarda çoklu ilaç direncine sahip bakteriyel enfeksiyonların tedavisinde faj tedavisi üzerinde durulmaktadır. Salgınlara, büyük mahsul ve ekonomik kayıplara yol açması nedeniyle ekili bitkileri enfekte eden virüsler de son derece incelenmiştir.

 Virüsler ilk olarak 19. yüzyılda, ekonomik açıdan önemli bir mahsul olan tütün bitkisinin gizemli bir hastalıktan etkilendiği ve daha sonra tütün mozaik virüsü olarak tanımlandığı zaman keşfedildi. Hayvan virüsleri hem veteriner araştırmalarında hem de tıbbi araştırmalarda büyük önem taşımaktadır. Ayrıca, virüsler, soğuk algınlığı, suçiçeği ve herpes hastalığından, sarı humma, Hepatit ve çiçek hastalığı gibi daha tehlikeli enfeksiyonlara kadar birçok insan hastalığının temelini oluşturur.

<h4>Bir Virüsün Yapısı</h4>

Virüsler hedef hücresine saldırmada uzmanlaşmış çeşitli şekillerde bulunurlar. Tüm virüslerin iki ana bileşeni viral genom ve koruyucu protein kat (kapsid) olarak bilinir. Viral genom, tek veya çift iplikçikli RNA veya DNA'dan oluşur ve kapsidi oluşturan proteinleri kodlar. Birlikte, viral genom ve kapsid nükleokapsid olarak bilinir.

Birçok ökaryotik virüsün benzersiz bir özelliği bir fosfolipid membran varlığıdır, ve bu yapı kapsidi çevreleyen bir zarf olarak adlandırılır. Bu zarf genellikle daha önce enfekte konak hücrelerinin membranlar kaynaklanır ama aynı zamanda viral proteinler içerebilir (zarf proteinleri denir). Son olarak, bazı hayvan virüsleri virüs tarafından kodlanmış proteinler, viral tegument, zarf ve kapsid arasındaki boşlukta bir küme içerir.

<h4>Viral Enfeksiyon</h4>

Viral yaşam döngüsü aşağıdaki beş adıma ayrılabilir: bağlanma, giriş, replikasyon, derleme ve salınım. Virüsün yüzeyindeki proteinler belirli konak hücrelerini tanımaya yardımcı olur. Bazı virüsler bu yüzey proteinlerini konak hücre reseptörlerini bağlamak ve endositoz ile içselleştirmeyi başlatmak için kullanırken, zarf kaplı virüsler doğrudan konak hücre zarı ile kaynaşabilir.

Bazı bakteriyofajlar hücreye girmez; genomlarını (ve viral enzimleri) konak hücreye enjekte ederler. Hücrenin içine girdikten sonra, virüs kaplanmamış ve konak hücrenin mekanizmalarını kendi genomunu çoğaltmaya yönlendirir. Konak hücre, viral genomun yeni kopyalarını paketleyerek, yeni nesiller üretir. Yeni nesil virüsler serbest bırakılmadan önce konak hücrede depolanabilir veya hücre zarından dışarı tomurcuklanma ile sürekli olarak hücreden ekstrüzyona uğrayabilir. Viral enfeksiyon döngüsü litik veya lisojenik olarak sınıflandırılır. Litik döngüde, yeni virüsler ana hücreden fırlar ve böylece onu öldürürler. Lisojenik döngüde, viral DNA, içinde bulunduğu konak genomuna dahil edilir ve konak hücre çoğaldıkça üretilir.

Virüsler Nelerdir?

Genel bakış

Bir virüs, bir protein kabuğu içine alınmış bir RNA veya DNA genomundan oluşan mikroskobik bir bulaşıcı parçacıktır. Üzerinde çoğalamıyor ...

Education

JoVE Core

Biology

Biyoloji

Genetics

Genetik

Viruses

Virüsler

KEY TERMS AND CONCEPTS

TEMEL TERİMLER VE KAVRAMLAR

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. The released viruses can then infect other cells.

Viruses can attack bacteria, plants, and animals. Viruses that infect bacteria are called bacteriophages, or phages, and they are very abundant. Scientists also study phages as a possible therapy for multidrug-resistant bacterial infections in humans. Plant viruses matter because outbreaks can cause major crop and economic losses.

Animal viruses are important in both veterinary research and medical research. Viruses were first discovered in the 19th century during studies of tobacco plants with a mysterious disease. That disease was later identified as Tobacco mosaic virus. Viruses are also linked to many human illnesses, including the common cold, chickenpox, herpes, yellow fever, hepatitis, and smallpox.

Viruses vary in shape, but they share two main parts: the viral genome and the capsid. The genome can be single-stranded or double-stranded RNA or DNA, and it carries the instructions for making capsid proteins. The genome and capsid together form the nucleocapsid. Many eukaryotic viruses also have an envelope, which is a phospholipid membrane often taken from a host cell. Some animal viruses also contain a tegument, a layer of viral proteins between the envelope and the capsid.

A viral infection usually follows five stages: attachment, entry, replication, assembly, and release. Viral surface proteins help the virus recognize the right host cell. Some viruses bind to host receptors and enter by endocytosis, while enveloped viruses can fuse with the host cell membrane. Some bacteriophages do not enter the cell at all. They inject their genome and viral enzymes into the host cell instead.

Once inside, the virus is uncoated and directs the host cell to copy and read its genetic material. The host cell packages the new genomes into viral particles to form progeny viruses. These progeny may stay in the cell for a time or leave by budding from the cell membrane. Viral infection can be lytic or lysogenic. In the lytic cycle, new viruses burst out and kill the host cell. In the lysogenic cycle, viral DNA becomes part of the host genome, stays dormant, and is copied when the host cell divides.

How Viruses Infect Cells and Multiply

what are viruses?

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

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...

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 viruses enter host cells, use cellular machinery to replicate, and spread through lytic and lysogenic cycles in plants, animals, and bacteria.

How Viruses Infect Cells and Multiply | JoVE K12

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Chromatin Position Affects Gene Expression

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Organization of Genes

Chromosome Structure

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HS-LS1-1

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HS-LS1-2

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Negative and Positive Feedback

Homeostatic Imbalance

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Homeostatic Imbalances in Body Temperature

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HS-LS1-3

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Cells Coordinate Growth and Proliferation

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Chromosome Duplication

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The Mitotic Spindle

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HS-LS1-4

How Viruses Infect Cells and Multiply

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