Chapter 07.3: What Mutations Tel Us About Gene Function

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biochemical pathway

Back 1

An orderly series of reactions that allows an organism to obtain simple molecules from the environment and convert them step by step into successively more complicated molecules

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auxotroph

Back 2

A mutant microorganism that can grow on minimal medium only if it has been supplemented with one or more growth factors not required by wild-type strains

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prototroph

Back 3

a microorganism (usually wild type) that can grow on minimal medium in the absence of one or more growth factors.

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amino acid

Back 4

the building blocks of proteins

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peptide bond

Back 5

a covalent bond that joins amino acids during protein synthesis

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dipeptide

Back 6

two amino acids connected by a peptide bond

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oligopeptide

Back 7

several amino acids linked by peptide bonds

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polypeptide

Back 8

amino-acid chains containing hundreds to thousands of amino acids joined by peptide bonds

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N terminus

Back 9

the end of a polypeptide chain that contains a free amino group that is not connected to any other amino acid

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C terminus

Back 10

the end of the polypeptide chain that contains a free carboxylic acid group

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missense mutation

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changes in that nucleotide sequence of a gene that change the identiy of an amino acid in the polypeptide encoded by that gene

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primary structure

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the linear sequence of amino acids within a polypeptide

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secondary structure

Back 13

localized region of a polypeptide chain with a characteristic geometry, such as an alpha-helix or beta-pleated sheet

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tertiary structure

Back 14

ultimate three-dimensional shape of a polypeptide

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denaturation

Back 15

the disruption of hydrogen bonds within a macromolecule that normally uses hydrogen bonds to maintain its structure and function.

Hydrogen bonds can be disrupted by heat, extreme conditions of pH, or exposure to chemicals such as urea. When normally soluble proteins are denatured, they unfold and expose their nonpolar amino acids, which can cause them to become insoluble. When DNA is denatured, double-stranded molecules break apart into two separate strands

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quaternary structure

Back 16

structure made up of the three-dimensional configuration of subunits in a multimeric protein