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19: Review of Molecular Genetics

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    3424

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    • 19.1: Polypeptides and Proteins
      Amino acids are the building blocks for proteins. There are 20 different amino acids commonly found in proteins. All amino acids contain an amino group and a carboxyl (acid) group. To form polypeptides and proteins, amino acids are joined together by peptide bonds, in which the amino of one amino acid bonds to the carboxyl (acid)  group of another amino acid. A peptide is two or more amino acids joined together by peptide bonds. Proteins are long chains of amino acids held by peptide bonds.
    • 19.2: Enzymes
      Enzymes are substances present in the cell in small amounts that function to speed up or catalyze chemical reactions so they occur fast enough to support life. On the surface of the enzyme is typically a small crevice that functions as an active site or catalytic site to which one or two specific substrates are able to bind. Anything that an enzyme normally combines with is called a substrate.
    • 19.3: Deoxyribonucleic Acid (DNA)
      Deoxyribonucleic acid (DNA) is a long, double-stranded, helical molecule composed of building blocks called deoxyribonucleotides. A deoxyribonucleotide is composed of 3 parts: a molecule of the 5-carbon sugar deoxyribose, a nitrogenous base, and a phosphate group. There are four nitrogenous bases found in DNA: adenine, guanine, cytosine, or thymine. Adenine and guanine are known as purine bases while cytosine and thymine are known as pyrimidine bases. Deoxyribose is a ringed 5-carbon sugar.
    • 19.4: DNA Replication in Prokaryotic Cells
      During DNA replication, each parent strand acts as a template for the synthesis of the other strand by way of complementary base pairing. Complementary base pairing refers to DNA nucleotides with the base adenine only forming hydrogen bonds with nucleotides having the base thymine (A-T). Likewise, nucleotides with the base guanine can hydrogen bond only with nucleotides having the base cytosine (G-C). Each DNA strand has two ends.
    • 19.5: DNA Replication in Eukaryotic Cells and the Eukaryotic Cell Cycle
      During DNA replication, each parent strand acts as a template for the synthesis of the other strand by way of complementary base pairing. Complementary base pairing refers to DNA nucleotides with the base adenine only forming hydrogen bonds with nucleotides having the base thymine (A-T). Likewise, nucleotides with the base guanine can hydrogen bond only with nucleotides having the base cytosine (G-C). Each DNA strand has two ends.
    • 19.6: Ribonucleic Acid (RNA)
      RNA is a single-stranded molecule composed of building blocks called ribonucleotides. A ribonucleotide is composed of 3 parts: a molecule of the sugar ribose, a nitrogenous base, and a phosphate group. RNA differs from DNA in several ways: RNA is single-stranded, not double-stranded; unlike DNA polymerases, RNA polymerases are able to join RNA nucleotides together without requiring a preexisting strand of RNA; RNA has the base uracil in place of thymine.
    • 19.7: Polypeptide and Protein Synthesis
      DNA is divided into functional units called genes. A gene is a segment of DNA that codes for a functional product (mRNA, tRNA, or rRNA). Since the vast majority of genes are transcribed into mRNA and mRNA is subsequently translated into polypeptides or proteins, most genes code for protein synthesis. In this section we will see how the sequence of deoxyribonucleotide bases along one strand of DNA ultimately codes for the amino acid sequence of a particular polypeptide or protein.
    • 19.8: Enzyme Regulation
      In living cells, there are hundreds of different enzymes working together in a coordinated manner. Living cells neither synthesize nor breakdown more material than is required for normal metabolism and growth. All of this necessitates precise control mechanisms for turning metabolic reactions on and off. Enzymes can be controlled or regulated in two ways: controlling the synthesis of the enzyme (genetic control) and controlling the activity of the enzyme (feedback inhibition).
    • 19.9: Mutation
      The sequence of deoxyribonucleotide bases in the genes that make up an organism's DNA determines the order of amino acids in the proteins and polypeptides made by that organism. A particular organism may possess alternate forms of some genes referred to as alleles. The physical characteristics an organism possesses, based on its genotype and the interaction with its environment, make up an organism's phenotype. Mutation is an error during DNA replication that results in a change in the sequence.
    • 19.E: Review of Molecular Genetics (Exercises)
      These are homework exercises to accompany Kaiser's "Microbiology" TextMap. Microbiology is the study of microorganisms, which are defined as any microscopic organism that comprises either a single cell (unicellular), cell clusters or no cell at all (acellular). This includes eukaryotes, such as fungi and protists, and prokaryotes. Viruses and prions, though not strictly classed as living organisms, are also studied.

    Thumbnail: DNA Double Helix. (Public Domain; Apers0n).

    This page titled 19: Review of Molecular Genetics is shared under a CC BY 4.0 license and was authored, remixed, and/or curated by Gary Kaiser via source content that was edited to the style and standards of the LibreTexts platform.