Virology Quiz on Viral Genetics and Life Cycle

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Questions and Answers

What is the primary genetic material that viruses can contain?

RNA only

Both DNA and RNA (correct)

Proteins

DNA only

What surrounds the viral genome?

Lipid bilayer

Cell membrane

Protein coat called capsid (correct)

Nuclear envelope

What is the estimated number of viruses present on the planet?

10 trillion

10 billion

10 million

10^31 (correct)

In terms of viral infection, what does 'tropism' refer to?

The specific types of cells a virus can infect within a host Signup and view all the answers

What characterizes viruses in relation to living organisms?

They require a host cell to replicate and utilize their genetic information. Signup and view all the answers

What is the role of the host cell in a viral life cycle?

It provides proteins and machinery for viral replication. Signup and view all the answers

How do large viruses like Mimivirus differ from smaller viruses?

They have a more complex structure and can perform translation. Signup and view all the answers

Which statement is true about the infection mechanism of viruses?

Viral infection is selective based on host range and tropism. Signup and view all the answers

What is the classification of Mimivirus in terms of its genetic content?

Contains 7 of the 67 universal genes Signup and view all the answers

Which of the following statements about the origin of viruses is considered a prediction?

Important enzymes in viruses should resemble those of their hosts. Signup and view all the answers

What is a common misconception about the classification of viruses?

Viruses should be included as a fifth domain of life. Signup and view all the answers

Which of the following best describes viral replication in enveloped viruses like HIV?

Occurs via fusion with the host cell membrane. Signup and view all the answers

What characteristic of viruses is illustrated by SARS-CoV-2?

It is a (+)ssRNA virus. Signup and view all the answers

What characteristic gives SARS-CoV-2 its crown-like appearance?

Spike, envelope, and membrane proteins Signup and view all the answers

What role do translation factors and tRNAs play in viruses like Mimivirus?

They are involved in translation and protein modification. Signup and view all the answers

Which of the following is NOT a cause of oncogenesis?

Bacterial infections Signup and view all the answers

What is a key distinction made about how viruses evolved?

They hijacked genes from true organisms. Signup and view all the answers

Why might some biologists argue that viruses are not alive?

They cannot carry out metabolic processes independently. Signup and view all the answers

How do viruses contribute to cancer development?

By affecting the host’s immune response or using viral genes Signup and view all the answers

What is the v-Src gene associated with?

Oncogenesis in RSV-infected cells Signup and view all the answers

Which aspect describes the process of oncogenesis?

Speeding up cell division without limits Signup and view all the answers

What do c-Src and v-Src genes have in common?

They have similar sequences but different functions Signup and view all the answers

What percentage of all human cancers is estimated to involve viral contributions?

20% Signup and view all the answers

Which statement accurately describes the proteins of SARS-CoV-2?

They are glycoproteins. Signup and view all the answers

What is the primary function of c-Src?

It acts as an enzyme that phosphorylates its targets. Signup and view all the answers

What distinguishes v-Src from c-Src?

v-Src lacks control in phosphorylation/de-phosphorylation. Signup and view all the answers

What role does the protein p53 play in cells?

It inhibits cell division in response to DNA damage. Signup and view all the answers

How do HPV E6/7 proteins contribute to cancer development?

By binding and inactivating p53. Signup and view all the answers

Which of the following definitions is accurate for proto-oncogenes?

Normal genes that can become cancerous if mutated. Signup and view all the answers

What is an oncogene?

A gene that can lead to unregulated cell division. Signup and view all the answers

What is the outcome of the accumulation of multiple mutations in proto-oncogenes and tumor suppressor genes?

It leads to the development of human cancers. Signup and view all the answers

Which type of mutation is primarily associated with the activation of oncogenes?

Mutations that can occur in regulatory sequences. Signup and view all the answers

Study Notes

Viruses, Their Life Cycle, and Cancer

Viruses are microscopic infectious agents containing DNA or RNA as genetic material.
Viral genomes are enclosed within a protein coat called a capsid.
Some viruses have an outer envelope composed of a lipid membrane and glycoproteins.
Viruses replicate solely inside a host cell, utilizing host cell machinery for their own functions.
The human population has recently experienced a global pandemic caused by a virus (COVID-19).
As of April 2024, approximately 7 million people worldwide had died from COVID-19.
An estimated 10³¹ viruses exist on Earth, which is significantly more than the number of stars in the universe.
Each virus typically infects only a few particular species.
The host specificity is called host range while the cell type a virus infects is called tropism.

Viruses as Agents of Cancer

Approximately 20% of human cancers are linked to viral infections.
Cancer can arise from a host’s response to a viral infection or from viral genes impacting the host cell.
Some viruses integrate their genetic material into host chromosomes, introducing oncogenes—cancer-causing genes.
These oncogenes can disrupt host cell functions related to cell division and lead to unregulated cell growth, resulting in tumors.

Viral Classification

Viruses are classified based on their nucleic acid type (DNA or RNA), capsid symmetry, and the presence or absence of an envelope.
Virus classification systems include Baltimore and others.
Viral classification factors such as genome type and nucleic acid symmetry.
An example of such classifications: groups I through VII for different kinds of viral genome structures.

Virus Life Cycles

Bacteriophages: Bacteriophages, viruses that infect bacteria, undergo either a lytic or lysogenic cycle, with lytic phages leading to host cell lysis.
Non-enveloped viruses (e.g., poliovirus): Viruses such as poliovirus adhere to cell receptors for entry; then, capsids are destroyed releasing viral RNA for replication.
Enveloped viruses (e.g., HIV, Zika virus): Entry can involve fusion with the host cell membrane or endocytosis.

Cancer-causing viruses and their associated tumors

Certain viruses, such as Epstein-Barr Virus (EBV), Hepatitis B/C virus (HBV/HCV), human herpes virus-8, and Human Immunodeficiency Virus (HIV), are known to contribute to various cancers.

Cellular Basis of Cancer

Cancer is a genetic disease arising from mutations in genes that control cell growth and division.
Oncogenesis produces tumors, clumps of rapidly-dividing cells that can invade surrounding tissues.
Cancer development may be caused by inherited mutations, DNA damage caused by environmental factors, and viral infections.
The cell cycle includes phases such as G0, G1, S, G2, and M.
Checkpoints during the cell cycle ensure precise progression through these phases.
Viruses like HPV can disrupt cell cycle regulation, leading to cancer development.
p53 is a tumor suppressor protein that detects DNA damage and stops cell division.
HPV E6/7 proteins block p53 activation, leading to uncontrolled cell division.

The Role of Proto-oncogenes and Tumor Suppressors

Proto-oncogenes are normal cellular genes that promote cell growth and division.
However, mutations in proto-oncogenes can convert them into oncogenes, which promote uncontrolled cell growth.
Tumor suppressor genes encode proteins that normally suppress cell division.
Mutations in tumor suppressor genes can lead to the loss of tumor suppression, resulting in uncontrolled cell growth.
Multiple mutations in both proto-oncogenes and tumor suppressor genes are frequently implicated in cancer development.

Mechanisms of Oncogenesis

The multiple-mutation model proposes that cancer development originates from multiple gene mutations.
This model highlights the accumulation of mutations (in proto-oncogenes and tumor suppressors) and their roles in driving cancer.
The various phases of the cell cycle, each with unique control points, are crucial for regulated cell division.

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Description

Test your knowledge on the fascinating world of viruses with this quiz focused on their genetic material, life cycles, and infection mechanisms. Explore concepts such as viral tropism and the structural differences among viruses. Perfect for biology students and virology enthusiasts!