Structure and Function of DNA Quiz

PDF page 426: The building blocks of nucleic acids are nucleotides. Nucleotides that compose DNA are called deoxyribonucleotides. The three components of a deoxyribonucleotide are a five-carbon sugar called deoxyribose, a phosphate group, and a nitrogenous base, a nitrogen-containing ring structure that is responsible for complementary base pairing between nucleic acid strands (Figure 10.11). The carbon atoms of the five-carbon deoxyribose are numbered 1ʹ, 2ʹ, 3ʹ, 4ʹ, and 5ʹ (1ʹ is read as “one prime”). A nucleoside comprises the five-carbon sugar and

PDF page 427: nitrogenous base—in this case, adenine. (b) The five carbons within deoxyribose are designated as 1ʹ, 2ʹ, 3ʹ, 4ʹ, and 5ʹ. The deoxyribonucleotide is named according to the nitrogenous bases (Figure 10.12). The nitrogenous bases adenine (A) and guanine (G) are the purines; they have a double-ring structure with a six-carbon ring fused to a five-carbon ring. The pyrimidines, cytosine (C) and thymine (T), are smaller nitrogenous bases that have only a sixcarbon ring structure.

PDF page 427: the single-ringed pyrimidines cytosine and thymine. Thymine is unique to DNA. Individual nucleoside triphosphates combine with each other by covalent bonds known as 5ʹ-3ʹ phosphodiester bonds, or linkages whereby the phosphate group attached to the 5ʹ carbon of the sugar of one nucleotide bonds to the hydroxyl group of the 3ʹ carbon of the sugar of the next nucleotide. Phosphodiester bonding between nucleotides forms the sugar-phosphate backbone, the alternating sugar-phosphate structure composing the framework of a nucleic acid strand (Figure 10.13). During the polymerization process, deoxynucleotide triphosphates (dNTP) are used. To construct the sugar-phosphate backbone, the two terminal phosphates are released from the dNTP as a pyrophosphate. The resulting strand of nucleic acid has a free phosphate group at the 5ʹ carbon end and a free hydroxyl group at the 3ʹ carbon end. The two unused phosphate groups from the nucleotide triphosphate are released as pyrophosphate during phosphodiester bond formation. Pyrophosphate is subsequently hydrolyzed, releasing the energy used to drive nucleotide polymerization.

PDF page 427: nitrogenous base—in this case, adenine. (b) The five carbons within deoxyribose are designated as 1ʹ, 2ʹ, 3ʹ, 4ʹ, and 5ʹ. The deoxyribonucleotide is named according to the nitrogenous bases (Figure 10.12). The nitrogenous bases adenine (A) and guanine (G) are the purines; they have a double-ring structure with a six-carbon ring fused to a five-carbon ring. The pyrimidines, cytosine (C) and thymine (T), are smaller nitrogenous bases that have only a sixcarbon ring structure.

PDF page 427: nitrogenous base—in this case, adenine. (b) The five carbons within deoxyribose are designated as 1ʹ, 2ʹ, 3ʹ, 4ʹ, and 5ʹ. The deoxyribonucleotide is named according to the nitrogenous bases (Figure 10.12). The nitrogenous bases adenine (A) and guanine (G) are the purines; they have a double-ring structure with a six-carbon ring fused to a five-carbon ring. The pyrimidines, cytosine (C) and thymine (T), are smaller nitrogenous bases that have only a sixcarbon ring structure.

PDF page 427: nitrogenous base—in this case, adenine. (b) The five carbons within deoxyribose are designated as 1ʹ, 2ʹ, 3ʹ, 4ʹ, and 5ʹ. The deoxyribonucleotide is named according to the nitrogenous bases (Figure 10.12). The nitrogenous bases adenine (A) and guanine (G) are the purines; they have a double-ring structure with a six-carbon ring fused to a five-carbon ring. The pyrimidines, cytosine (C) and thymine (T), are smaller nitrogenous bases that have only a sixcarbon ring structure.

PDF page 426: In Microbial Metabolism, we discussed three classes of macromolecules: proteins, lipids, and carbohydrates. In this chapter, we will discuss a fourth class of macromolecules: nucleic acids. Like other macromolecules, nucleic acids are composed of monomers, called nucleotides, which are polymerized to form large strands. Each nucleic acid strand contains certain nucleotides that appear in a certain order within the strand, called its base sequence. The base sequence of deoxyribonucleic acid (DNA) is responsible for carrying and retaining the hereditary information in a cell. In Mechanisms of Microbial Genetics, we will discuss in detail the ways in which DNA uses its own base sequence to direct its own synthesis, as well as the synthesis of RNA and proteins, which, in turn, gives rise to products with diverse structure and function. In this section, we will discuss the basic structure and function of DNA.

PDF page 427: the single-ringed pyrimidines cytosine and thymine. Thymine is unique to DNA. Individual nucleoside triphosphates combine with each other by covalent bonds known as 5ʹ-3ʹ phosphodiester bonds, or linkages whereby the phosphate group attached to the 5ʹ carbon of the sugar of one nucleotide bonds to the hydroxyl group of the 3ʹ carbon of the sugar of the next nucleotide. Phosphodiester bonding between nucleotides forms the sugar-phosphate backbone, the alternating sugar-phosphate structure composing the framework of a nucleic acid strand (Figure 10.13). During the polymerization process, deoxynucleotide triphosphates (dNTP) are used. To construct the sugar-phosphate backbone, the two terminal phosphates are released from the dNTP as a pyrophosphate. The resulting strand of nucleic acid has a free phosphate group at the 5ʹ carbon end and a free hydroxyl group at the 3ʹ carbon end. The two unused phosphate groups from the nucleotide triphosphate are released as pyrophosphate during phosphodiester bond formation. Pyrophosphate is subsequently hydrolyzed, releasing the energy used to drive nucleotide polymerization.

PDF page 427: the single-ringed pyrimidines cytosine and thymine. Thymine is unique to DNA. Individual nucleoside triphosphates combine with each other by covalent bonds known as 5ʹ-3ʹ phosphodiester bonds, or linkages whereby the phosphate group attached to the 5ʹ carbon of the sugar of one nucleotide bonds to the hydroxyl group of the 3ʹ carbon of the sugar of the next nucleotide. Phosphodiester bonding between nucleotides forms the sugar-phosphate backbone, the alternating sugar-phosphate structure composing the framework of a nucleic acid strand (Figure 10.13). During the polymerization process, deoxynucleotide triphosphates (dNTP) are used. To construct the sugar-phosphate backbone, the two terminal phosphates are released from the dNTP as a pyrophosphate. The resulting strand of nucleic acid has a free phosphate group at the 5ʹ carbon end and a free hydroxyl group at the 3ʹ carbon end. The two unused phosphate groups from the nucleotide triphosphate are released as pyrophosphate during phosphodiester bond formation. Pyrophosphate is subsequently hydrolyzed, releasing the energy used to drive nucleotide polymerization.

PDF page 427: the single-ringed pyrimidines cytosine and thymine. Thymine is unique to DNA. Individual nucleoside triphosphates combine with each other by covalent bonds known as 5ʹ-3ʹ phosphodiester bonds, or linkages whereby the phosphate group attached to the 5ʹ carbon of the sugar of one nucleotide bonds to the hydroxyl group of the 3ʹ carbon of the sugar of the next nucleotide. Phosphodiester bonding between nucleotides forms the sugar-phosphate backbone, the alternating sugar-phosphate structure composing the framework of a nucleic acid strand (Figure 10.13). During the polymerization process, deoxynucleotide triphosphates (dNTP) are used. To construct the sugar-phosphate backbone, the two terminal phosphates are released from the dNTP as a pyrophosphate. The resulting strand of nucleic acid has a free phosphate group at the 5ʹ carbon end and a free hydroxyl group at the 3ʹ carbon end. The two unused phosphate groups from the nucleotide triphosphate are released as pyrophosphate during phosphodiester bond formation. Pyrophosphate is subsequently hydrolyzed, releasing the energy used to drive nucleotide polymerization.

PDF page 428: Chargaff (1905–2002) examined the content of DNA in different species and discovered that adenine, thymine, guanine, and cytosine were not found in equal quantities, and that it varied from species to species, but not between individuals of the same species. He found that the amount of adenine was very close to equaling the amount of thymine, and the amount of cytosine was very close to equaling the amount of guanine, or A = T and G = C. These relationships are also known as Chargaff’s rules. Other scientists were also actively exploring this field during the mid-20th century. In 1952, American scientist Linus Pauling (1901–1994) was the world’s leading structural chemist and odds-on favorite to solve the structure of DNA. Pauling had earlier discovered the structure of protein α helices, using X-ray diffraction, and, based upon X-ray

PDF page 429: British researchers Rosalind Franklin (1920–1958) and her graduate student R.G. Gosling were also using X-ray diffraction to understand the structure of DNA (Figure 10.14). It was Franklin’s scientific expertise that resulted in the production of more well-defined X-ray diffraction images of DNA that would clearly show the overall doublehelix structure of DNA.

PDF page 428: Chargaff (1905–2002) examined the content of DNA in different species and discovered that adenine, thymine, guanine, and cytosine were not found in equal quantities, and that it varied from species to species, but not between individuals of the same species. He found that the amount of adenine was very close to equaling the amount of thymine, and the amount of cytosine was very close to equaling the amount of guanine, or A = T and G = C. These relationships are also known as Chargaff’s rules. Other scientists were also actively exploring this field during the mid-20th century. In 1952, American scientist Linus Pauling (1901–1994) was the world’s leading structural chemist and odds-on favorite to solve the structure of DNA. Pauling had earlier discovered the structure of protein α helices, using X-ray diffraction, and, based upon X-ray

PDF page 428: diffraction images of DNA made in his laboratory, he proposed a triple-stranded model of DNA. At the same time,