Biology Quiz: Monocots, Viruses & Bacteria

HIV and AIDS

• HIV, the human immunodeficiency virus, causes AIDS, acquired immunodeficiency syndrome.
• 1981: A large number of Kaposi's cancer cases were seen in the US.
• 1983: HIV was identified as the virus causing AIDS.

HIV: A Retrovirus

• HIV is a retrovirus, meaning it has RNA as its genetic material.
• HIV infects CD4 molecules and coreceptors such as fusin and CCR5.

Retroviruses (RNA Virus)

• Retroviruses utilize reverse transcriptase to convert their RNA into DNA.
• This viral DNA can be integrated into the host cell's genome.
• The high mutation rate of retroviruses contributes to their ability to evolve and survive.
• Viral RNA enters the host cell with reverse transcriptase.
• The enzyme reverse transcriptase copies the viral RNA into DNA.
• The reverse transcribed viral DNA is integrated into the host cell's genome.

Pathology of HIV

• Two major HIV strains are HIV-1 and HIV-2.
• HIV primarily infects helper T cells in the immune system.
• Helper T cells typically activate other white blood cells to produce antibodies.

T-Cells

• T-cells are a type of white blood cell (leukocyte).
• The thymus is responsible for maturing T-cells to fight infections.
• "T" stands for thymus.

HIV Infection Progression (Graph)

• Infection is indicated by minor symptoms like swollen lymph nodes.
• Relative antibody concentration and helper T-cell concentration decrease over time.
• Loss of immune function occurs as characteristic diseases like yeast infections develop and progress to AIDS.

Challenges with AIDS vaccines

• HIV is a retrovirus that integrates viral DNA into host DNA.
• HIV has a high mutation rate.
• HIV attacks the body's defense system.

Modes of Transmission

• Sexual intercourse
• Sharing needles
• Through breast milk
• From mother to child during childbirth

Thought Question

• In the 1980s, there was a sudden emergence of AIDS cases among hemophiliacs. This was because hemophiliacs received contaminated blood products.

Bacteriophage Reproduction

• Bacteriophages are viruses that infect bacteria.
• The bacteriophage life cycle can follow either a lytic or lysogenic path.

Bacteriophage Structure

• These viruses have a more complex structure compared to other viruses.
• The head is a naked icosahedral capsid.
• The tail is a sheath with fibers at its end.

Bacteriophage Life Cycle Overview

• Lytic cycle: Adsorption, Penetration, Prophage Formation, Spontaneous Induction, Replication and Maturation, Release
• Lysogenic cycle: Includes steps 1, 2, 3, and 4 but Prophage Formation, Replication, and Release occur afterward.

The Lytic Cycle

• Summary of the lytic cycle: Adsorption; Entry/Penetration; Replication; Assembly of new components; Lysis of host cell & release of virions.

Adsorption of a Bacteriophage to the Cell Wall of the Bacterium

• Proteins on the viral surface attach to a specific receptor on the host cell's surface.

Penetration of the Viral Genome into the Cytoplasm of the Bacterium

• The viral genome (DNA or RNA) enters the host cell.

Viral Replication and Maturation

• Viral DNA is transcribed and translated by the host cell.
• Protein parts are assembled inside the host cell.

Release of the Bacteriophages by Lysis of the Bacterium

• Fully formed viruses burst from the host cell by lysing it.

Lytic Cycle Summary

• Adsorption, Entry penetration, Replication, Assembly of new components, Lysis of host cell and release of virions.

The Lysogenic Cycle

• Adsorption, Entry, Integration, Spontaneous induction, Replication, Assembly, Lysis and release.

Comparing the two Reproductive Strategies

• Lytic vs. Lysogenic cycles in bacteriophages.

Central Dogma

• DNA = Original instructions, genetic information.
• RNA = Copy of information, a message.
• Protein = Building blocks of life, worker molecules.
• Transcription: DNA → RNA.
• Translation: RNA → Proteins.

DNA viruses

• Viral DNA integrates into the host cell's genome.
• Transcription of host cell DNA results in transcription of viral DNA along with it.
• Viral RNA is translated to form viral proteins that assemble to form new virions.

Herpes

• Herpes simplex 1 and 2 can be accompanied by symptoms, including headaches, fever, flu-like symptoms, pain, itching, tingling, and tenderness around genitals.

Chicken Pox (Varicella-zoster virus)

• VZV, chickenpox virus, can cause lesions on the body.

RNA viruses

• Viral RNA is immediately translated with host cell's machinery after skipping transcription.
• Ribosomes bind to all types of RNA (host and viral).
• Ribosomes translate RNA to protein.
• The viral proteins form the virion (new virus).

Retroviruses

• Retroviruses have an enzyme that reverse transcribes RNA into DNA. This viral DNA is then integrated into the host cell's genome. The high mutation rate increases retroviruses' ability to evolve and survive.

Retrovirus Replication

• Absorption to specific receptor, endocytosis; uncoating; reverse transcription; transport to nuclear membrane; transcription; translation; assembly; budding.

Viruses

• Viruses are microscopic infectious agents composed of nucleic acid and a protein coat.
• They can only replicate within a host cell.

Classification

• Viruses are classified by shape (spherical, cylindrical, polyhedral).
• Polio virus is polyhedral.
• Tobacco mosaic virus (TMV) is cylindrical.
• HIV is spherical.

Polio

• Polio virus enters through the mouth, damages the nervous system causing paralysis.
• Immunization prevents polio infection.

Protists

• Protists are eukaryotes, not classified as plants, animals, fungi, or prokaryotes
• Some are unicellular, some multicellular. ,
• Undergo primarily asexual reproduction (Spores),
• Generally like humid environments.

Protists: Importance

• Protists play a major role as a food chain base impacting other organisms.
• They participate in symbiotic relationships.
• Some protists are responsible for "red tides".

3 Groups of Protists

• Plant-like protists (Algae): Aquatic and contain chloroplasts.
• Animal-like protists (Protozoa): Heterotrophic.
• Fungi-like protists (Slime molds and Water molds): Heterotrophic.

Malaria

• Malaria is caused by a parasite spread by mosquitos

Classification System

• The classification of living organisms, from broad categories (kingdom, phylum) to more specific ones (species)
• Includes levels of taxonomic hierarchy like kingdom, phylum, class, order, family, genus, and species.

Binomial Nomenclature

• A two-word system of naming organisms based on genus and species.

Dichotomous Key

• A tool used to identify organisms based on a series of pairs of characteristics leading to a unique name.

Homologous Structures

• Similar structures that indicate common ancestry.

Prokaryotic vs. Eukaryotic Cells

• Prokaryotes lack a nucleus and membrane-bound organelles, while eukaryotes possess both.

Bacterial Shapes

• Cocci (round), Bacilli (rod-shaped), and Spirilla (spiral-shaped)

Bacterial Cell Wall Structure

• Gram-positive bacteria have a thick peptidoglycan layer, while gram-negative have a thin layer.

Antibiotics and Antibiotic Resistance

• Antibiotics are useful in fighting bacterial diseases, but bacterial resistance is a growing challenge.

Bacterial Reproduction: Asexual, Sexual, Spores

• Asexual reproduction (binary fission): One parent, identical offspring.
• Sexual reproduction (conjugation): Mating bridge between cells, genetic recombination.
• Spore formation: A resistant dormant form, can survive harsh conditions, then develop into a new organism under favorable conditions.

Comparing Reproductive Strategies

• Table comparing advantages and disadvantages of asexual, sexual, and spore-forming reproduction strategies in bacteria (and possibly other organisms).

Kingdoms of Life

• Table summarizing differences between the six kingdoms of life.

Viruses

• Viruses are not considered living organisms outside a host cell. They are inert and rely on host cells for replication.

Test your knowledge on the characteristics of monocotyledons and dicotyledons, as well as important concepts related to viral cycles and bacterial classification. This quiz covers various aspects of plant biology, virology, and microbiology, allowing you to assess your understanding of these essential topics.