DNA: The Chemical Nature of the Gene Benjamin A. Pierce GENETICS A Conceptual Approach FIFTH EDITION CHAPTER 10 DNA: The Chemical Nature of the Gene © 2014 W. H. Freeman and Company

Saqqaq people: lived in Greenland; DNA sequenced from hair tufts from 4000-year-old male; found the sequences matched those from the Chukchis from Russia.

Genetic Material Possesses Several Key Characteristics Genetic material must contain complex information. Genetic material must replicate faithfully. Genetic material must encode the phenotype. Genetic material must have the capacity to vary.

All Genetic Information Is Encoded in the Structure of DNA or RNA Early studies of DNA Figure 10.1 Miescher: nuclein Kossel: DNA contains four nitrogenous bases Chargaff’s rules

All Genetic Information Is Encoded in the Structure of DNA or RNA DNA as the source of genetic information Identification of the transforming principle Griffith experiment Figure 10.2 Drs. Avery, Macleod, and McCarty’s experiment Figure 10.3 The Hershey–Chase experiment Figure 10.4

Figure 10.2 Griffith’s experiments demonstrated transformation in bacteria.

Figure 10.3 Avery, MacLeod, and McCarty’s experiment revealed the nature of the transforming principle. 9

Concept Check 1 If Avery, Macleod, and McCarty had found that samples of heat-killed bacteria treated with RNase and DNase transformed bacteria, but samples treated with protease did not, what conclusion would they have made? Protease carries out transformation. RNA and DNA are the genetic materials. Protein is the genetic material. RNase and DNase are necessary for transformation.

Concept Check 1 If Avery, Macleod, and McCarty had found that samples of heat-killed bacteria treated with RNase and DNase transformed bacteria, but samples treated with protease did not, what conclusion would they have made? Protease carries out transformation. RNA and DNA are the genetic materials. Protein is the genetic material. RNase and DNase are necessary for transformation.

All Genetic Information Is Encoded in the Structure of DNA or RNA DNA as the source of genetic information Watson and Crick’s discovery of the three-dimensional structure of DNA X-ray diffraction image of DNA Figure 10.6

Figure 10.6 X-ray diffraction provides information about the structures of molecules.

All Genetic Information Is Encoded in the Structure of DNA or RNA RNA as genetic information: In most organisms, DNA carries genetic information; in some, RNA carries genetic information instead Tobacco Mosaic Virus Figure 10.8

Figure 10.8 Fraenkel-Conrat and Singer’s experiment demonstrated that RNA in the tobacco mosaic virus carries the genetic information.

Figure 10.8 Fraenkel-Conrat and Singer’s experiment demonstrated that RNA in the tobacco mosaic virus carries the genetic information.

The primary structure of DNA: DNA Consists of Two Complementary and Antiparallel Nucleotide Strands that Form a Double Helix The primary structure of DNA: Deoxyribonucleotides Nucleotides Three parts: sugar, a phosphate, and a base Nucleotide structure: Figure 10.9 Purine or pyrimidine base: Figure 10.10

Figure 10.12 There are four types of DNA nucleotides.

Secondary structure of DNA: DNA Consists of Two Complementary and Antiparallel Nucleotide Strands that Form a Double Helix Secondary structure of DNA: The double helix Backbone formed through phosphodiester bonds Hydrogen bond and base pairing Antiparallel complementary DNA strands Figure 10.13

Figure 10.13 DNA and RNA consist of polynucleotide strands.

Figure 10.13 DNA and RNA consist of polynucleotide strands.

Figure 10.13 DNA and RNA consist of polynucleotide strands.

Figure 10.13 DNA and RNA consist of polynucleotide strands.

Figure 10.13 DNA and RNA consist of polynucleotide strands.

Figure 10.13 DNA and RNA consist of polynucleotide strands.

Concept Check 3 The antiparallel nature of DNA refers to: its charged phosphate groups. the pairing of bases on one strand with bases on the other strand. the formation of hydrogen bonds between bases from opposite strands. the opposite direction of the two strands of nucleotides.

Concept Check 3 The antiparallel nature of DNA refers to: its charged phosphate groups. the pairing of bases on one strand with bases on the other strand. the formation of hydrogen bonds between bases from opposite strands. the opposite direction of the two strands of nucleotides.

Secondary structure of DNA: DNA Consists of Two Complementary and Antiparallel Nucleotide Strands that Form a Double Helix Secondary structure of DNA: Three-dimensional structure identified by Watson and Crick refers to B-DNA Figure 10.14 Different secondary structures: Figure 10.15

Figure 10.15 DNA can assume several different secondary structures.

Special Structure Can Form in DNA and RNA Hairpin structure: in single strands of nucleotides, when sequences of nucleotides on the same strand are inverted complements, a hairpin structure will be formed. Figure 10.17 (a) When the complementary sequences are contiguous, the hairpin has a stem but no loop. Figure 10.17 (b) RNA molecules may contain numerous hairpins, allowing them to fold up into complex structures. Figure 10. 17 (c)

Figure 10.17 (a) A DNA secondary structure - hairpin

Figure 10.17 (b) A DNA secondary structure - stem

Figure 10. 17 (c) Secondary structure of RNA component of RNase P of E Figure 10.17 (c) Secondary structure of RNA component of RNase P of E. coli.

Special Structure Can Form in DNA and RNA H-DNA: three-stranded (triplex); formed when DNA unwinds and one strand pairs with double-stranded DNA from another part of the molecule Often occurs in long sequences of only purines or only pyrimidines Common in mammalian genomes

Special Structure Can Form in DNA and RNA DNA methylation Methyl groups added to nucleotide bases Related to gene expression in eukaryotes Affects the three-dimensional structure of DNA