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Nucleic Acids

Nucleic Acids. Concept 5.5: Nucleic acids store and transmit hereditary information. The amino acid sequence of a polypeptide is programmed by a unit of inheritance called a gene Genes are made of DNA, a nucleic acid. The Roles of Nucleic Acids. There are two types of nucleic acids:

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Nucleic Acids

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  1. Nucleic Acids

  2. Concept 5.5: Nucleic acids store and transmit hereditary information • The amino acid sequence of a polypeptide is programmed by a unit of inheritance called a gene • Genes are made of DNA, a nucleic acid

  3. The Roles of Nucleic Acids • There are two types of nucleic acids: • Deoxyribonucleic acid (DNA) • Ribonucleic acid (RNA) • DNA provides directions for its own replication • DNA directs synthesis of messenger RNA (mRNA) and, through mRNA, controls protein synthesis • Protein synthesis occurs in ribosomes

  4. LE 5-25 DNA Synthesis of mRNA in the nucleus mRNA NUCLEUS CYTOPLASM mRNA Movement of mRNA into cytoplasm via nuclear pore Ribosome Synthesis of protein Amino acids Polypeptide

  5. The Structure of Nucleic Acids • Nucleic acids are polymers called polynucleotides • Each polynucleotide is made of monomers called nucleotides • Each nucleotide consists of a nitrogenous base, a pentose sugar, and a phosphate group • The portion of a nucleotide without the phosphate group is called a nucleoside

  6. LE 5-26a 5¢ end Nucleoside Nitrogenous base Phosphate group Pentose sugar Nucleotide 3¢ end Polynucleotide, or nucleic acid

  7. Nucleotide Monomers • Nucleotide monomers are made up of nucleosides and phosphate groups • Nucleoside = nitrogenous base + sugar • There are two families of nitrogenous bases: • Pyrimidines have a single six-membered ring • Purines have a six-membered ring fused to a five-membered ring • In DNA, the sugar is deoxyribose • In RNA, the sugar is ribose

  8. LE 5-26b Nitrogenous bases Pyrimidines Uracil (in RNA) U Cytosine C Thymine (in DNA) T Purines Guanine G Adenine A Pentose sugars Deoxyribose (in DNA) Ribose (in RNA) Nucleoside components

  9. Nucleotide Polymers • Nucleotide polymers are linked together, building a polynucleotide • Adjacent nucleotides are joined by covalent bonds that form between the –OH group on the 3´ carbon of one nucleotide and the phosphate on the 5´ carbon on the next • These links create a backbone of sugar-phosphate units with nitrogenous bases as appendages • The sequence of bases along a DNA or mRNA polymer is unique for each gene

  10. The DNA Double Helix • A DNA molecule has two polynucleotides spiraling around an imaginary axis, forming a double helix • In the DNA double helix, the two backbones run in opposite 5´ to 3´ directions from each other, an arrangement referred to as antiparallel • One DNA molecule includes many genes • The nitrogenous bases in DNA form hydrogen bonds in a complementary fashion: A always with T, and G always with C

  11. LE 5-27 5¢ end 3¢ end Sugar-phosphate backbone Base pair (joined by hydrogen bonding) Old strands Nucleotide about to be added to a new strand 5¢ end New strands 5¢ end 3¢ end 5¢ end 3¢ end

  12. DNA and Proteins as Tape Measures of Evolution • The linear sequences of nucleotides in DNA molecules are passed from parents to offspring • Two closely related species are more similar in DNA than are more distantly related species • Molecular biology can be used to assess evolutionary kinship

  13. The Theme of Emergent Properties in the Chemistry of Life: A Review • Higher levels of organization result in the emergence of new properties • Organization is the key to the chemistry of life

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