Bio 20A, Chapter 4., Nucleic Acids And The Origin Of Life

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nucleic acid

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A polymer made up of nucleotides, specialized for the storage, transmission, and expression of genetic information. DNA and RNA are nucleic acids.

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DNA (deoxyribonucleic acid)

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The fundamental hereditary material of all living organisms. In eukaryotes, stored primarily in the cell nucleus. A nucleic acid using deoxyribose rather than ribose. It is used to specify the amino acid sequences of proteins.

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RNA (ribonucleic acid)

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An often single stranded nucleic acid whose nucleotides use ribose rather than deoxyribose and in which the base uracil replaces thymine found in DNA. Serves as genome from some viruses.

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nucleotide

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Consist of a pentose sugar, a phosphate group, and a nitrogen-containing base. They are the monomers that form nucleic acids.

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base

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In nucleic acids, the purine or pyrimidine that is attached to each sugar in the sugar-phosphate backbone.

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pyrimidine

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One of the two types of nitrogenous bases in nucleic acids. Each of the pyrimidines—cytosine, thymine, and uracil—pairs with a specific purine. They have a six-membered single-ring structure.

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purine

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One of the two types of nitrogenous bases in nucleic acids. Each of the purines—adenine and guanine—pairs with a specific pyrimidine. They have a fused double-ring structure.

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deoxyribose

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A five-carbon sugar found in nucleotides and DNA. Differs from ribose found in RNA by the absence of one oxygen atom.

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ribose

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A five-carbon sugar in nucleotides and RNA.

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phosphodiester linkages

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The connection in a nucleic acid strand, formed by linking two nucleotides. Joined by the sugar of one nucleotide and the phosphate of the next.

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diester

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refers to the two covalent bonds formed by –OH groups reacting with acidic phosphate groups.

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adenine (A)

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A nitrogen-containing base found in nucleic acids, ATP, NAD, and other compounds.

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cytosine (C)

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A nitrogen-containing base found in DNA and RNA.

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guanine (G)

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A nitrogen-containing base found in DNA, RNA, and GTP.

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thymine (T)

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Nitrogen-containing base found in DNA.

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uracil (U)

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A pyrimidine base found in nucleotides of RNA.

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complementary base pairing

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The AT (or AU), TA (or UA), CH, and GC pairing of bases in double-stranded DNA, in transcription, and between tRNA and mRNA.

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double helix

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Refers to DNA and the (usually right-handed) coil configuration of two complementary, antiparallel strands.

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DNA replication

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the ability of DNA to reproduce itself exactly.

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transcription

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the process whereby DNA copies its information into RNA.

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translation

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the process whereby the nucleotide sequence in RNA specifies a sequence of amino acids in a polypeptide.

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genome

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The complete DNA sequence for a particular organism or individual.

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gene

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A unit of heredity. Used here as the unit of genetic function which carries the information for a single polypeptide or RNA.

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What percentage of the chimpanzee base sequence is shared with humans?

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98%

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ATP

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adenosine triphosphate; acts as an energy transducer in many biochemical reactions.

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transduce

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to convert energy from one form to another.

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GTP

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guanosine triphosphate – serves as an energy source in protein synthesis.

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cAMP

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cyclic adenosine monophosphate – a special nucleotide in which an additional bond forms between the sugar and phosphate group.

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Frencesco Redi

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an early scientist who debunked spontaneous generation in the 17th century by keeping jars of meat, some of which were exposed to air and developed flies, where others weren't and did not have flies.

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When did Earth form?

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4.6 BYA

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When did life first appear on Earth?

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3.8 BYA

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chemical evolution

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The theory that life originated through the chemical transformation of inanimate substances.

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When did oxygen first accumulate in the atmosphere?

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2.6 BYA

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Miller-Urey experiment

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A 1950s experiment at the University of Chicago which used an “atmosphere” similar to that of early Earth, which then produced all five bases, 17 of the 20 amino acids, and 3- to 6- carbon sugars. Ribose was not present.

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ribozymes

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An RNA molecule with catalytic activity.

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cell

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The simplest structural unit of a living organism. In multicellular organisms, the building blocks of tissues and organs.

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membrane

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a barrier that regulates what goes in and out of the cell.

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How is the lipid bilayer formed?

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formed as hydrophobic fatty acids “huddle” together. When water is trapped in the inside, they stabilize by forming a second layer of fatty acid along the inside wall.

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protocells

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Early compartmentalization of amphipathic fatty acids forming lipid bilayers. Neither RNA or DNA can pass through this layer, but sugars and nucleotides can. Nucleic acids can replicate using nucleotides from outside. This can all take place without protein catalysis.