3.3 DNA Structure 3.3.1 – 3.3.5

Concept 5.5: Nucleic acids store, transmit, and help express 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 made of monomers called nucleotides © 2011 Pearson Education, Inc.

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 on ribosomes © 2011 Pearson Education, Inc.

DNA 1 Synthesis of mRNA mRNA NUCLEUS CYTOPLASM Figure 5.25-1 DNA 1 Synthesis of mRNA mRNA NUCLEUS CYTOPLASM Figure 5.25 DNA → RNA → protein.

Movement of mRNA into cytoplasm Figure 5.25-2 DNA 1 Synthesis of mRNA mRNA NUCLEUS CYTOPLASM mRNA 2 Movement of mRNA into cytoplasm Figure 5.25 DNA → RNA → protein.

Movement of mRNA into cytoplasm Ribosome Figure 5.25-3 DNA 1 Synthesis of mRNA mRNA NUCLEUS CYTOPLASM mRNA 2 Movement of mRNA into cytoplasm Ribosome Figure 5.25 DNA → RNA → protein. 3 Synthesis of protein Amino acids Polypeptide

The Components 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 one or more phosphate groups The portion of a nucleotide without the phosphate group is called a nucleoside © 2011 Pearson Education, Inc.

Figure 5.26 Components of nucleic acids. Sugar-phosphate backbone 5 end Nitrogenous bases Pyrimidines 5C 3C Nucleoside Nitrogenous base Cytosine (C) Thymine (T, in DNA) Uracil (U, in RNA) Purines 5C 1C Phosphate group 3C 5C Sugar (pentose) Adenine (A) Guanine (G) 3C (b) Nucleotide Figure 5.26 Components of nucleic acids. Sugars 3 end (a) Polynucleotide, or nucleic acid Deoxyribose (in DNA) Ribose (in RNA) (c) Nucleoside components

Nitrogenous base Phosphate group Sugar (pentose) Figure 5.26ab Sugar-phosphate backbone 5 end 5C 3C Nucleoside Nitrogenous base 5C 1C Figure 5.26 Components of nucleic acids. Phosphate group 3C Sugar (pentose) 5C 3C (b) Nucleotide 3 end (a) Polynucleotide, or nucleic acid

3.3.1 Outline DNA nucleotide structure.

3.3.2 State the names of the four bases in DNA

Nucleoside = nitrogenous base + sugar There are two families of nitrogenous bases Pyrimidines (cytosine, thymine, and uracil) have a single six-membered ring Purines (adenine and guanine) have a six-membered ring fused to a five-membered ring In DNA, the sugar is deoxyribose; in RNA, the sugar is ribose Nucleotide = nucleoside + phosphate group © 2011 Pearson Education, Inc.

(c) Nucleoside components Figure 5.26c Nitrogenous bases Pyrimidines Cytosine (C) Thymine (T, in DNA) Uracil (U, in RNA) Sugars Purines Figure 5.26 Components of nucleic acids. Deoxyribose (in DNA) Ribose (in RNA) Adenine (A) Guanine (G) (c) Nucleoside components

Nucleotide Polymers Nucleotide polymers are linked together to build 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 © 2011 Pearson Education, Inc.

The Structures of DNA and RNA Molecules RNA molecules usually exist as single polypeptide chains DNA molecules have two polynucleotides spiraling around an imaginary axis, forming a double helix In the DNA double helix, the two backbones run in opposite 5→ 3 directions from each other, an arrangement referred to as antiparallel One DNA molecule includes many genes © 2011 Pearson Education, Inc.

3.3.3 Outline how DNA nucleotides are linked together by covalent bonds into a single strand

Called complementary base pairing The nitrogenous bases in DNA pair up and form hydrogen bonds: adenine (A) always with thymine (T), and guanine (G) always with cytosine (C) Called complementary base pairing Complementary pairing can also occur between two RNA molecules or between parts of the same molecule In RNA, thymine is replaced by uracil (U) so A and U pair © 2011 Pearson Education, Inc.

Base pair joined by hydrogen bonding Figure 5.27 5 3 Sugar-phosphate backbones Hydrogen bonds Base pair joined by hydrogen bonding Figure 5.27 The structures of DNA and tRNA molecules. Base pair joined by hydrogen bonding 3 5 (a) DNA (b) Transfer RNA

3.3.4 Explain how DNA double Helix is formed using complementary bases pairing and hydrogen bonding Chargoff’s Rule

3.3.5 Draw and label a simple diagram of the molecular structure of DNA

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 © 2011 Pearson Education, Inc.

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 © 2011 Pearson Education, Inc.

Figure 5.UN02 Summary table, Concepts 5.2–5.5

Figure 5.UN02a Summary table, Concepts 5.2–5.3

Figure 5.UN02b Summary table, Concepts 5.4–5.5