5: Nucleic Acids
- Page ID
- 178788
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- 5.1: Prelude to Nucleic Acids
- In the 1970s, an intense research effort began that eventually led to the production of genetically engineered human insulin—the first genetically engineered product to be approved for medical use. To accomplish this feat, researchers first had to determine how insulin is made in the body and then find a way of causing the same process to occur in nonhuman organisms, such as bacteria or yeast cells. Many aspects of these discoveries are presented in this chapter on nucleic acids.
- 5.2: Nucleotides
- Nucleotides are composed of phosphoric acid, a pentose sugar (ribose or deoxyribose), and a nitrogen-containing base (adenine, cytosine, guanine, thymine, or uracil). Ribonucleotides contain ribose, while deoxyribonucleotides contain deoxyribose.
- 5.3: Nucleic Acid Structure
- DNA is the nucleic acid that stores genetic information. RNA is the nucleic acid responsible for using the genetic information in DNA to produce proteins. Nucleotides are joined together to form nucleic acids through the phosphate group of one nucleotide connecting in an ester linkage to the OH group on the third carbon atom of the sugar unit of a second nucleotide. Nucleic acid sequences are written starting with the nucleotide having a free phosphate group (the 5′ end).
- 5.4: Replication and Expression of Genetic Information
- In DNA replication, each strand of the original DNA serves as a template for the synthesis of a complementary strand. DNA polymerase is the primary enzyme needed for replication. In transcription, a segment of DNA serves as a template for the synthesis of an RNA sequence. RNA polymerase is the primary enzyme needed for transcription. Three types of RNA are formed during transcription: mRNA, rRNA, and tRNA.
- 5.5: Protein Synthesis and the Genetic Code
- In translation, the information in mRNA directs the order of amino acids in protein synthesis. A set of three nucleotides (codon) codes for a specific amino acid.
- 5.6: Mutations and Genetic Diseases
- The nucleotide sequence in DNA may be modified either spontaneously or from exposure to heat, radiation, or certain chemicals and can lead to mutations. Mutagens are the chemical or physical agents that cause mutations. Genetic diseases are hereditary diseases that occur because of a mutation in a critical gene.
- 5.7: Viruses
- Viruses are very small infectious agents that contain either DNA or RNA as their genetic material. The human immunodeficiency virus (HIV) causes acquired immunodeficiency syndrome (AIDS).
- 5.8: Nucleic Acids (Summary)
- To ensure that you understand the material in this chapter, you should review the meanings of the bold terms in the following summary and ask yourself how they relate to the topics in the chapter.
- 5.9: Nucleic Acids (Exercises)
- Problems and select solutions for the chapter.