unit 4.5

Are viruses cells?

No, they are noncellular infectious particles.

What is the host range of a virus?

The types of organisms a virus can infect.

What is tissue tropism?

Preference of a virus for specific tissues in the host.

What are viruses made of?

Nucleic acid (DNA or RNA) and a protein capsid.

What is a capsid?

The protein coat surrounding viral genetic material.

What is a viral envelope?

A membrane taken from the host cell surrounding some viruses.

What nucleic acids can viruses have?

dsDNA, ssDNA, dsRNA, ssRNA.

Do viruses have metabolic activity outside hosts?

No, they are metabolically inert.

What enzyme do retroviruses have?

Reverse transcriptase.

What does reverse transcriptase do?

Makes DNA from an RNA genome.

What is the first virus discovered?

Tobacco Mosaic Virus.

What is viral replication dependent on?

Hijacking the host's transcription and translation machinery.

Do RNA viruses mutate quickly?

Yes, due to error-prone replication.

What is the Baltimore classification based on?

Viral genome type and replication strategy.

What are bacteriophages?

Viruses that infect bacteria.

What is the lytic cycle?

Viral cycle where host is lysed and new viruses released.

What is the lysogenic cycle?

Viral DNA integrates into the host genome as a prophage.

What is a prophage?

Viral DNA integrated into bacterial DNA.

What triggers a prophage to enter the lytic cycle?

Stress conditions.

What are acute infections?

Rapid onset infections with sudden symptoms.

What are persistent infections?

Chronic or latent viral infections.

What cells does HIV infect?

CD4+ T helper cells and macrophages.

Why is HIV deadly?

It destroys immune cells, allowing opportunistic infections.

Is HIV a retrovirus?

Yes, it uses reverse transcriptase to integrate into host DNA.

What are prions?

Misfolded proteins that cause neurodegenerative disease.

What diseases do prions cause?

Mad cow disease, scrapie, CJD.

What are viroids?

Small circular RNA molecules that infect plants.

What does 'antigenic drift' refer to in influenza?

Small mutations in HA and NA proteins.

What does 'antigenic shift' refer to?

Reassortment of viral genomes creating new strains.

Why do we need a new flu vaccine each year?

Antigenic drift changes viral surface proteins.

What type of virus is West Nile?

Enveloped ssRNA arbovirus.

What is SARS-CoV-2?

The coronavirus that causes COVID-19.

What does a vaccine do?

Stimulates immune memory using a non-virulent form of a pathogen.

What is recombinant DNA?

A DNA molecule made from two different sources.

What enzyme cuts DNA at specific sequences?

Restriction endonucleases.

What type of restriction enzyme is used in biotechnology?

Type II restriction enzymes.

What do Type II restriction enzymes recognize?

Specific palindromic DNA sequences.

What do sticky ends allow?

Base pairing between DNA fragments cut with the same enzyme.

What enzyme seals DNA fragments together?

DNA ligase.

What is a cloning vector?

A DNA molecule (like a plasmid) used to carry foreign DNA into a host.

What features must a plasmid vector have?

Origin of replication, selectable marker, restriction sites.

What does reverse transcriptase do?

Makes DNA from an RNA template.

What is cDNA?

Double-stranded DNA made from mature mRNA.

Why is cDNA useful?

It contains only coding regions (no introns).

What is a DNA library?

A collection of cloned DNA fragments kept inside host cells.

What is a cDNA library?

A library of only the expressed genes from a cell or tissue.

What does PCR do?

Amplifies a specific DNA sequence.

What are the 3 steps of PCR?

Denaturation, annealing, extension.

Why is Taq polymerase used in PCR?

It is heat-stable and survives high temperatures.

How does gel electrophoresis separate DNA?

By size: small fragments move faster toward the positive pole.

What does RFLP stand for?

Restriction Fragment Length Polymorphism.

What is DNA fingerprinting based on?

Variation in STR (short tandem repeat) lengths.

What is CRISPR-Cas9 used for?

Precise genome editing by cutting specific DNA sequences.

What guides Cas9 to its target?

A guide RNA complementary to the DNA sequence.

What is a transgenic organism?

An organism containing a gene from another species.

What vector is commonly used to genetically modify plants?

Ti plasmid from Agrobacterium tumefaciens.

What is Bt toxin?

A natural insecticidal protein from Bacillus thuringiensis used in GM crops.

What is Golden Rice engineered to produce?

β-carotene (vitamin A precursor).

What is bioremediation?

Use of microorganisms to break down environmental pollutants.

What is biofuel made from?

Biomass such as algae or plant oils.

What medical product is commonly made using genetic engineering?

Human insulin.

What are embryonic stem cells?

Pluripotent cells capable of forming all adult cell types.

What are adult stem cells?

Multipotent cells that replace specific tissues.

What are induced pluripotent stem (iPS) cells?

Differentiated cells reprogrammed to behave like ES cells.

What is organismal cloning?

Making a genetically identical copy of an organism.

What technique produced Dolly the sheep?

Nuclear transplantation into an enucleated egg.