DNA vs RNA: Key Differences

DNA and RNA Differences

• DNA is a double-stranded molecule with a long chain of nucleotides arranged in a helix.
• RNA is a single-stranded molecule with a shorter chain of nucleotides.
• DNA contains deoxyribose sugar, and RNA has ribose sugar.
• DNA has the nitrogenous bases thymine, adenine, cytosine, and guanine.
• RNA has the nitrogenous bases uracil, cytosine, adenine, and guanine.
• DNA is located in the nucleus and mitochondria of a cell.
• RNA is located in the cytoplasm, nucleus, and ribosome.
• DNA functions in the transmission of genetic information and long-term storage.
• RNA is critical for transmitting the genetic code necessary for protein creation from the nucleus to the ribosome
• In DNA, guanine pairs with cytosine (G-C), and adenine pairs with thymine (A-T).
• In RNA, guanine pairs with cytosine (G-C), and adenine pairs with uracil (A-U).
• Inside cells, DNA is organized into chromosomes within the nucleus.
• A gene is a segment of DNA.

DNA Transcription

• DNA transcription is the process of RNA synthesis
• The direction of transcription is 5' to 3'.

RNA Translation

• RNA translation results in the production of proteins

Viruses

• Viruses are the smallest biological particles, with the tiniest only 20 nm in diameter.
• Viruses consist of strands of DNA or RNA surrounded by a protective protein coat called a capsid.
• Viruses are not biological organisms and are not classified in any kingdom of living things.
• Viruses lack organelles.
• Viruses cannot perform physiological and metabolic functions like respiration or digestion.
• Viruses become active only when they invade a cell and are completely inert outside a host cell.
• Viruses multiply only in living cells.
• Viruses are classified based on their type of genetic material (DNA or RNA).
• Viruses are classified according their shape or structural features.
• Viruses are classified according to their replication properties.
• Viruses are classified according to the diseases they cause.
• The shape of a virus is determined by the type and arrangement of proteins in its capsid.
• Viruses pathogenic to humans are classified into 21 groups.
• Bacteriophages are viruses that attack bacteria and infect bacterial cells.

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 higher mutation rates than DNA viruses due to the error-prone nature of RNA replication.
• RNA viruses higher mutation rates make it more difficult to produce effective vaccines against them.

Viral Replication

• The lytic and lysogenic cycles are two methods of viral replication

Lytic Viral Replication

• The virus attaches to specific receptors on the host cell.
• The virus injects its nucleic acid into the host cell, or if enveloped, the host cell phagocytosizes the entire virus particle.
• If enveloped, the virus breaks out of the vacuole, then releases its nucleic acid into the cell
• The virus's nucleic acid directs the host cell to replicate the viral DNA or RNA.
• New virus particles are assembled.
• The virus directs the production of an enzyme that damages the host cell wall, causing it to swell and burst, releasing the newly formed virus particles.

Lysogenic Viral Replication

• The virus attaches to specific receptors on the host cell.
• Entry to the cell is similar to the lytic cycle
• The viral nucleic acid is not replicated but integrated into the host cell's chromosome as a prophage.
• The host cell reproduces normally, with subsequent cell divisions containing the original father cell's chromosome embedded with the prophage.
• Certain factors determine whether the daughter cell undergoes the lytic or lysogenic cycle.
• A cell undergoing the lysogenic cycle can switch to the lytic cycle.

Retroviruses

• A retrovirus uses RNA as its genomic material.
• Retroviral RNA is converted into DNA, which is inserted it into the DNA of the host cell upon infection
• The cell then produces more retroviruses, which infect other cells.
• Many retroviruses are associated with diseases.
• Human immunodeficiency virus (HIV), causes AIDS.

Retrovirus Replication

• Forces RNA into a cell.
• Reverse transcriptase enzymes catalyze the synthesis of DNA 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 as a provirus and never leaves the host cell, unlike a prophage.
• The infected host cell undergoes the lytic or lysogenic cycle.

Differences Between Eukaryotes, Prokaryotes, and Viruses

• Eukaryotes examples include plants, animals, fungi, and algae.
• Prokaryotes examples include bacteria.
• Viruses examples include HIV, Ebola, and Smallpox.
• Eukaryotes have a nucleus, prokaryotes and viruses do not.
• Eukaryotes and the nucleic acid (DNA) in chromosomes is found in the nucleus.
• Prokaryotes contains circular DNA scattered in the cytoplasm.
• Viruses contain DNA/RNA held in a protein coat (capsid) .
• Eukaryotes are unicellular or multicellular
• Prokaryotes are all unicellular
• Viruses are microscopic particles (too small to be seen).
• Eukaryotes and prokaryotes have a cell membrane and cytoplasm
• Viruses lack a defined cell membrane and cytoplasm.
• Eukaryotes contains membrane-bound organelles
• Prokaryotes lack membrane-bound organelles.
• Viruses lack membrane-bound organelles
• Eukaryotes Contains a cell wall in plants (Cellulose) and fungi (chitin).
• Prokaryotes has a cell wall made up of peptidoglycan and glycoproteins.
• Viruses lack a cell wall.