General Biology 2: Viruses, Prokaryotes, Protists, and Plant Evolution

Comprehensive practice flashcards in fill-in-the-blank style covering all lecture topics from viral biology, prokaryotic genetics, protistan diversity and life cycles, to embryophyte and plant evolution.

All viruses possess a core of nucleic acid surrounded by a protein coat called a __________.

capsid

The viral capsid is composed of repeating protein subunits of __________ to a few proteins.

one

In addition to a capsid, some viruses are surrounded by an envelope composed of lipids and __________.

proteins

Because viruses lack cytoplasm and organelles, they are not classified as __________.

cells

The nucleic acid core of a virus can be either DNA or __________.

RNA

The viral nucleic acid strand structure may be linear or __________.

circular

Most DNA viruses possess genomes that are __________-stranded.

double

Coronaviruses possess a single-stranded __________ genome.

RNA

Retroviruses encode their genes as RNA but replicate via a __________ intermediate.

DNA

The HIV genome consists of two identical single-stranded __________ molecules.

RNA

When a virus particle exists outside of a host cell, it is referred to as a __________.

virion

Outside of a living host cell, virions are metabolically __________.

inert

Retroviruses carry the specialized enzyme __________ transcriptase inside their virion.

reverse

Reverse transcriptase synthesizes a molecule of __________ using viral RNA as a template.

DNA

Because they cannot reproduce outside of host cells, viruses are described as obligate intracellular __________.

parasites

The variety of organisms that a virus can infect is known as its __________ range.

host

The affinity of a virus for infecting specific tissue types within a host is known as tissue __________.

tropism

Deformed Wing Virus is transmitted to western honey bees (Apis mellifera) by the parasitic mite __________.

Varroa jacobsoni

Deformed Wing Virus causes severe developmental pathology in Apis mellifera, but is harmless in the eastern honey bee named __________.

Apis cerana

Deformed Wing Virus exerts its pathological action primarily during __________ development in honey bees.

wing

The parasitic mite Varroa jacobsoni is capable of transmitting at least __________ different honey bee viruses.

$$20$$

Viruses hijack host cellular machinery because they completely lack their own ribosomes, amino acids, ATP, tRNAs, and __________.

nucleotides

Viruses that specifically infect bacterial cells are called __________.

bacteriophages

The best-studied bacteriophages infect Escherichia coli and include the __________ series.

T

Viruses have also been identified infecting the domain __________, exhibiting distinct structures from bacteriophages.

Archaea

In the bacteriophage __________ cycle, the viral reproductive process culminates in host cell lysis and death.

lytic

In the bacteriophage __________ cycle, viral DNA integrates stably into the host bacterium's genome without immediately killing it.

lysogenic

A bacteriophage genome that has integrated into a bacterial chromosome is called a __________.

prophage

The process by which a prophage excises from the bacterial chromosome in response to cell stress is called __________.

induction

Human Immunodeficiency Virus (HIV) is the causative agent of __________.

Acquired Immune Deficiency Syndrome (AIDS)

AIDS was first clinically reported in the United States in the year __________.

$$1981$$

Genetic evidence indicates that HIV originated in Africa during the __________.

1950s

HIV originated from multiple independent zoonotic jumps from __________ Immunodeficiency Virus (SIV).

Simian

Because HIV strains arose from multiple independent transmissions from simians to humans, HIV as a group represents an example of __________ rather than a single monophyletic clade.

homoplasy

HIV-1 groups M, N, and O originated from jumps into humans from SIV strains infecting __________.

chimpanzees

HIV-2 strains A and B jumped to humans from SIV infecting the __________ mangabey.

sooty

HIV selectively targets immune cells carrying the __________ cell-surface receptor protein.

CD4

The two primary cell types infected by HIV are helper T cells and __________.

macrophages

Clinical symptoms of AIDS typically appear following an asymptomatic or latent period of __________ to 10 years.

$$8$$

Viral DNA that is integrated into the host eukaryotic genome during HIV infection is called a __________.

provirus

The HIV surface glycoprotein that attaches to the host CD4 receptor is __________.

gp120

HIV requires binding to CD4 and a coreceptor such as __________ or CXCR4 to enter human immune cells.

CCR5

Individuals possessing a mutation in the human gene encoding the __________ coreceptor are resistant to HIV infection.

CCR5

Each of the two identical single-stranded RNA molecules in the HIV genome is __________ nucleotides in length.

$$9749$$

HIV can enter host cells via endocytosis or via __________ surface internalization.

cell

During cell surface internalization, the viral envelope fuses directly with the host __________ membrane.

plasma

The enzyme reverse transcriptase is notorious for being extremely __________-prone during viral genome replication.

error

High mutation rates generated by reverse transcriptase make it extremely difficult to develop an effective HIV __________.

vaccine

HIV DNA is inserted into the host chromosome by the viral enzyme __________.

integrase

New HIV virions are released from the host cell through a process called __________.

budding

The primary mechanism causing CD4+ T cell death during HIV infection is a form of programmed cell death called __________.

pyroptosis

Pyroptosis in HIV-infected CD4+ cells is triggered when reverse transcriptase generates __________ viral DNA.

incomplete

In addition to pyroptosis, infected CD4+ T cells are destroyed by other cells of the host __________ system.

immune

The FDA lists __________ antiretroviral drugs approved for use in AIDS therapy.

$$32$$

Antiretroviral drugs target viral entry, viral replication, viral DNA integration, or protein __________.

maturation

Drugs that inhibit the viral maturation of polypeptides are called __________ inhibitors.

protease

Antiretroviral treatment combining multiple drugs is known as HAART, which stands for __________ active antiretroviral therapy.

highly

Since its introduction in the mid-1990s, HAART has cut the U.S. AIDS death rate by __________-fourths.

three

If HAART combination therapy is stopped, viral loads in the patient's blood __________ again.

rise

Coronaviruses belong to the viral order __________.

Nidovirales

The family containing coronaviruses is named __________.

Coronaviridae

Coronaviruses are classified into the subfamily __________.

Orthocoronavirinae

The subfamily Orthocoronavirinae contains four genera: Alphacoronavirus, Betacoronavirus, Gammacoronavirus, and __________.

Deltacoronavirus

SARS-CoV-2 belongs to the coronavirus genus named __________.

Betacoronavirus

The SARS-CoV-2 genome is a single-stranded RNA molecule containing approximately __________ nucleotides.

$$30{,}000$$

The RNA genome of SARS-CoV-2 encodes __________ total proteins.

$$20$$

Of the proteins encoded by SARS-CoV-2, __________ are structural proteins.

four

The four structural proteins of SARS-CoV-2 are the Spike (S), Envelope (E), Membrane (M), and __________ (N) proteins.

Nucleocapsid

The Spike (S) protein gene of SARS-CoV-2 has a length of approximately __________ base pairs.

$$3800$$

Non-structural proteins (NSPs) encoded by the coronavirus genome include an RNA replicase and a viral __________.

protease

The SARS-CoV-2 Spike protein binds specifically to the human cell-surface receptor named __________.

ACE2

The most common route of entry for SARS-CoV-2 into host cells is cell surface __________.

internalization

A critical mutation of __________ nucleotides in length in the Spike protein gene made SARS-CoV-2 highly aggressive and pandemic.

$$12$$

The sequence of the 12-nucleotide insertion in the SARS-CoV-2 Spike gene is __________.

CCUCGGCGGGCA

Unlike HIV, replication of the SARS-CoV-2 genome occurs entirely in the host cell cytoplasm and never produces __________.

DNA

The genome of SARS-CoV-2 never enters the host cell's __________.

nucleus

In Dr. Ortega's exam anxiety survey, action 1 states that __________% of the exam questions come from the Weekly Quizzes.

$$50$$

In Dr. Ortega's course survey, the exam reflection survey awards each student __________ extra credit points.

$$4$$

In the Exam 1 reflection survey, __________% of respondents strongly agreed that weekly quizzes helped them learn and prepare.

$$60$$

Prokaryotes were the only cellular forms of life abundant on Earth for over __________ billion years before eukaryotes appeared.

one

Currently, less than __________% of all prokaryotic species are scientifically known and described.

$$10$$

Together, Bacteria and Archaea represent at least __________% of all organismal lineages on Earth.

$$70$$

All prokaryotes strictly require __________ to survive.

water

Prokaryotes are divided into two domains: Bacteria and __________.

Archaea

Tuberculosis, cholera, tetanus, diphtheria, pneumonia, and bubonic plague are all caused by organisms in the domain __________.

Bacteria

Because Bacteria and Archaea share a common ancestor that is also ancestral to Eukarya, prokaryotes form a __________ group.

paraphyletic

Most prokaryotes possess a single circular chromosome made of __________-stranded DNA.

double

As an exception to the single-chromosome rule, the bacterium Vibrio cholerae possesses __________ circular chromosomes.

two

Small, circular, accessory double-stranded DNA molecules found commonly in prokaryotes are called __________.

plasmids

In Archaea, the plasma membrane lipids contain an __________ linkage between glycerol and hydrophobic tails.

ether

In Bacteria and Eukarya, membrane phospholipids have an __________ linkage between glycerol and fatty acids.

ester

The hydrophobic hydrocarbon tails of Archaea membranes are branched with __________ groups.

H3-CH3

Unlike Archaea, the hydrophobic fatty acid chains of Bacteria and Eukarya are __________.

unbranched

Ether linkages and branched hydrophobic tails are considered derived evolutionary novelties or __________ for Archaea.

synapomorphies

Bacterial cell walls are reinforced by a rigid carbohydrate-protein polymer called __________.

peptidoglycan

Peptidoglycan consists of repeating carbohydrate polymers cross-linked by short bridges of __________.

peptides

The rigid peptidoglycan cell wall prevents bacterial cells from swelling and lysing in __________ environments.

hypotonic

A hypotonic environment contains a __________ concentration of solutes compared to the bacterial cytoplasm.

lower

Archaea cell walls lack peptidoglycan and instead contain a structurally similar molecule known as __________.

pseudomurein

Gram-positive bacteria have a cell wall characterized by a __________ layer of peptidoglycan.

thick