DNA vs RNA

• DNA and RNA are chains of nucleotides

DNA

• A double-stranded molecule arranged in a helix structure
• Each strand is a polymer of subunits called nucleotides
• Each nucleotide contains a phosphate, a 5-carbon deoxyribose sugar, and a nitrogenous base
• The four bases are adenine, thymine, cytosine and guanine
• Stores genetic information in humans
• Located in the cell's nucleus
• Only present in DNA viruses
• DNA contains deoxyribose sugar
• DNA's nitrogenous base pairings are guanine with cytosine (G-C) and adenine with thymine (A-T)
• Transmits genetic information and acts as a medium for long-term storage

RNA

• A single-stranded molecule and polymer of subunits called nucleotides
• Each strand is a polymer of subunits called nucleotides
• Each nucleotide contains a phosphate, a 5-carbon ribose sugar, and a nitrogenous base
• The four bases are adenine, uracil, cytosine, and guanine
• Translates genetic information into proteins in humans
• Located outside the cell's nucleus, in the cytoplasm
• Stores genetic information in some viruses
• RNA contains ribose sugar
• RNA's nitrogenous base pairings are guanine with cytosine (G-C) and adenine with uracil (A-U)
• Critical for the transmission of the genetic code to enable necessary protein creation

DNA Transcription (RNA Synthesis)

• The direction of transcription is (5'-3')

RNA Translation

• During translation is where mRNA creates proteins

Viruses

• The smallest biological particle, with the tiniest being 20 nm in diameter
• Strands of DNA or RNA surrounded by a protective protein coat called a capsid
• Classified based on their type of genetic material (DNA or RNA), shape/structural features, replication properties, and the diseases they cause
• Shape is determined by the type and arrangement of proteins in the capsid
• Pathogenic to humans and are classified into 21 groups
• Can also attack bacteria and infects bacterial cells and are called bacteriophages
• Not biological organisms and are not classified in any kingdom of living things
• Lack organelles and the ability to perform physiological and metabolic functions (respiration, digestion, etc.)
• Only come to life when they invade a cell and viruses multiply only in living cells
• Outside of a host cell, viruses are completely inert

Viral Genome - DNA Viruses

• Herpes
• Smallpox
• Hepatitis
• Adenoviruses
• Warts

Viral Genome - RNA Viruses

• HIV
• Polio virus
• Hepatitis C
• Ebola
• SARS
• Influenza
• 70% of all viruses are RNA viruses
• RNA viruses have much higher mutation rates than DNA viruses because of the error-prone process of RNA replication with host cell enzymes and organelles, that makes it difficult to produce effective vaccines against them.

Viral Replication - Lytic

• Attachment: Binds to specific receptors on the host cell
• Entry: Virus injects its nucleic acid or the host cell phagocytosises the entire virus particle into a vacuole.
• Replication: The virus's nucleic acid instructs the host cell to replicate the virus’s DNA or RNA
• Assembly: New virus particles are assembled.
• Lysis and Release: The virus directs the production of an enzyme which damages the host cell wall, causing the host cell to swell and burst.

Viral Replication - Lysogenic

• Attachment: The virus binds to specific receptors on the host cell
• Entry: Similar to lytic cycle
• Incorporation: The viral nucleic acids is integrated into the host cell's chromosome and known as a prophage.
• Host Cell Reproduction: The host cell reproduces normally where daughter cells contain the original father cell's chromosome embedded with a prophage
• Cycle Induction: Factors determine whether the daughter cell undergoes either the lytic or lysogenic cycle and can switch to the lytic cycle at any time.

Retrovirus

• A virus that uses RNA as its genomic material
• Upon infection, a cell converts the retroviral RNA into DNA, which in turn is inserted into the DNA of the host cell
• Causes the cell to produce more retroviruses, which infect other cells
• Many retroviruses are associated with diseases, one being HIV (causes AIDS)

Retrovirus replication

• The retrovirus forces RNA into the cell
• Reverse transcriptase enzymes catalyze the synthesis of a DNA strand complementary to the viral RNA
• Reverse transcriptase catalyzes a second DNA strand complementary to the first, creating double-stranded DNA
• The DNA is incorporated into the host cell's chromosomes
• The incorporated DNA is called a provirus, and it does not leave the host cell

Differences between Eukaryotes, Prokaryotes and Viruses

• Eukaryotes: Plants, Animals, Fungi, Algae, Presence of nucleus, DNA in chromosomes found in the nucleus, Unicellular and Multicellular, Present cell membrane and cytoplasm, Presence of membrane-bound organelles, and Present cell wall in plants and fungi
• Prokaryotes: Bacteria, Absence of nucleus, DNA is circular and scattered in cytoplasm, All Unicellular, Present cell membrane and cytoplasm, Absence of membrane-bound organelles, and Present but made up of peptidoglycan and glycoproteins cell wall
• Viruses: HIV, Ebola, Smallpox, Absence of nucleus, DNA/RNA held in protein coat (capsid), Microscopic particles, Lack defined Cell membrane and cytoplasm, Absence of membrane-bound organelles, and Absent cell wall