Chapter 4 - Nucleic Acids and The Origin of Life

• What are the two main chemical signatures of life being searched for on Mars?

  Presence of water and carbon-based chemistry
• What is the role of nucleic acids in living organisms?

  Nucleic acids are specialized for storage, transmission, and use of genetic information
• What are the two types of nucleic acids?

  DNA and RNA
• What are the monomers of nucleic acids?

  Nucleotides, which consist of a pentose sugar, nitrogenous base, and phosphate group
• What is the difference between DNA and RNA in terms of sugar?

  DNA contains deoxyribose, while RNA contains ribose
• What are the two forms of nitrogenous bases found in nucleic acids?

  Pyrimidines and purines
• How are nucleotides linked together in nucleic acids?

  Nucleotides are linked by phosphodiester bonds
• In which direction do nucleic acids grow?

  Nucleic acids grow in the 5′-to-3′ direction
• What are the purines found in DNA?

  Adenine (A) and Guanine (G)
• What are the pyrimidines found in DNA?

  Cytosine (C) and Thymine (T)
• What is complementary base pairing in nucleic acids?

  Purines pair with pyrimidines by hydrogen bonds
• How does RNA differ from DNA in terms of structure?

  RNA is single-stranded, while DNA forms a double helix
• What base does RNA have instead of thymine?

  Uracil (U)
• What is the process of transcription?


  Transcription is when DNA sequences are copied into RNA
• What is the process of translation?


  Translation is when RNA sequence specifies the sequence of amino acids in a polypeptide
• What is gene expression?

  Gene expression is the combined process of transcription and translation
• What is a genome?


  The complete set of DNA in an organism
• What are the other roles of nucleotides besides forming nucleic acids?

  ATP for energy transfer, GTP for protein synthesis, and cAMP for hormone action
• Who first disproved spontaneous generation?

  Francesco Redi
• What did Louis Pasteur's experiments show?

  Microorganisms can arise only from other microorganisms
• What are the two main theories about the origin of life?

  Chemical evolution and life came from outside Earth
• What is chemical evolution?

  Chemical evolution is the theory that conditions on primitive Earth led to the formation of simple molecules that led to life
• What gases did Miller and Urey use in their experiments?

  H₂, NH₃, CH₄, and H₂O
• What did the Miller and Urey experiments demonstrate?

  The experiments demonstrated that simple organic molecules could form under primitive Earth conditions
• What role do volcanoes play in the origin of life?

  Volcanoes may have added gases like CO₂, N₂, H₂S, and SO₂ to the atmosphere
• What is the hypothesis regarding life coming from outside Earth?

  Some meteorites contain molecules suggesting that living organisms might have reached Earth within a meteorite
• What is the hypothesis being tested regarding Martian soil?

  The hypothesis is that Martian soil can show chemical changes consistent with life
• What method is used to test Martian soil for evidence of life?

  Soils are exposed to nutrients labeled with radioisotopes and checked for radioactive gases
• What is the next step in the chemical evolution theory?


  A plausible explanation of how polymers formed
• What is the role of catalysts in the origin of life?

  Catalysts, such as proteins called enzymes, are key to the origin of life
• What is the "RNA World" hypothesis?

  The hypothesis suggests that RNA may have been the first catalyst for its own replication and protein synthesis
• What evidence supports the "RNA World" hypothesis?

  Ribose can be formed in prebiotic chemical synthesis experiments, and ribozymes catalyze peptide linkages
• What are protocells?


  Protocells are organized systems of parts that allow small molecules to pass through and can replicate
• What evidence was found in 3.5 billion-year-old rocks in Australia?

  Evidence of cells that appeared to be cyanobacteria capable of photosynthesis
• What is the significance of carbon isotopes in fossils?

  Carbon isotopes indicate photosynthesis and the presence of various types of bacteria
• How long did it take for the first cells to appear after the formation of Earth?

  About 500 million to 1 billion years
• What is the goal of NASA regarding life on Mars?

  Finding evidence for current or past life on Mars
• What did the Curiosity rover detect in Martian soil in 2018?

  Complex organic compounds
• What is the purpose of the Mars Sample Return mission?

  To bring Martian soil samples to Earth for experimentation
• What other celestial bodies are planned for investigation for signs of life?

  Jupiter’s Europa and Saturn’s Enceladus and Titan