Untitled Flashcards Set

Alkaptonuria: An autosomal recessive trait with altered metabolism of homogentisic acid. Affected individuals do not produce the enzyme to metabolize this acid.

Amino acid: One of the 20 subunits of proteins. Each contains an amino group, a carboxyl group, and an R group.

Codon: Triplets of nucleotides in mRNA that encode information for a specific amino acid in a protein.

Stop codon: A codon in mRNA that signals the end of translation. UAA, UAG, and UGA are stopcodons.

Start codon: A codon present in mRNA that signals the location for translation to begin. The codon AUG functions as a start codon and codes for the amino acid methionine.

pre-messenger RNA (pre-mRNA): The transcript made from the DNA template that is processed and modified to form messenger RNA.

Transcription: Transfer of genetic information from the base sequence of DNA to the base sequence of RNA brought about by RNA synthesis.

Messenger RNA (mRNA): A single-stranded complementary copy of the nucleotide sequence in a gene.

Translation: Conversion of information encoded in the nucleotide sequence on an mRNA molecule into the linear sequence of amino acids in a protein.

Promoter: A regulatory region located at the beginning of a gene.

Introns: DNA sequences present in some genes that are transcribed but are removed during processing and therefore are not present in mature mRNA.

Exons: DNA sequences that are transcribed, joined to other exons during mRNA processing, and translated into the amino acid sequence of a protein.

Cap: A modified base (guanine nucleotide) that is attached to the 5′ end of eukaryotic mRNA molecules.

Poly-A tail: A series of A nucleotides added to the 3′ end of mRNA molecules.

R group: Each amino acid has a different side chain, called an R group. An R group can be positively or negatively charged or neutral.

Amino group: A chemical group (NH2) found in amino acids and at one end of a polypeptide chain.

Carboxyl group: A chemical group (COOH) found in amino acids and at one end of a polypeptide chain.

Essential amino acids: Those amino acids that cannot be synthesized by the body and must be included in the diet.

Polypeptide: A molecule made of amino acids joined together by peptide bonds.

N-terminus: The end of a polypeptide or protein that has a free amino group.

C-terminus: The end of a polypeptide or protein that has a free carboxyl group.

Ribosomes: Cytoplasmic particles that aid in the production of proteins.

Ribosomal RNA (rRNA): RNA molecules that form part of the ribosome.

Transfer RNA (tRNA): A small RNA molecule that contains a binding site for a specific type of amino acid and a three-base segment known as an anticodon that recognizes a specific base sequence in messenger RNA.

Anticodon: A group of 3 nucleotides in a tRNA molecule that pairs with a complementary sequence (known as a codon) in an mRNA molecule.

Initiation complex: Formed by the combination of mRNA, tRNA, and the small ribosome subunit. The first step in translation.

Peptide bond: A covalent chemical link between the carboxyl group of one amino acid and the amino group of another amino acid.

Polysomes: A messenger RNA (mRNA) molecule with several ribosomes attached.

Chaperone: A protein that guides the folding of a polypeptide into a functional, three-dimensional shape, converting the polypeptide into a protein.

Proteome: The set of proteins present in a particular cell at a specific time under a particular set of conditions.

Primary structure: The amino acid sequence in a polypeptide chain.

Secondary structure: The pleated or helical structure in a protein molecule generated by the formation of bonds between amino acids.

Tertiary structure: The three dimensional structure of a protein molecule brought about by folding on itself.

Quaternary structure: The structure formed by the interaction of two or more polypeptide chains in a protein.

Prion: A protein folded into an infectious conformation that is the cause of several disorders, including Creutzfeldt-Jakob disease and mad-cow disease.

Mad-cow disease: A prion disease of cattle, also known as bovine spongiform encephalopathy, or BSE.

Chromatin remodeling: The set of chemical changes to the DNA and histones that activate and inactivate gene expression.

RNA interference (RNAi): A mechanism of gene regulation that controls the amounts of mRNA available for translation.

Substrate: The specific chemical compound that is acted on by an enzyme.

Product: The specific chemical compound that is the result of enzymatic action. In biochemical pathways, a compound can serve as the product of one reaction and the substrate for the next reaction.

Metabolism: The sum of all biochemical reactions by which cells convert and utilize energy.

Inborn error of metabolism: The concept advanced by Archibald Garrod that many genetic traits result from alterations in biochemical pathways.

Essential amino acids: Amino acids that cannot be synthesized in the body and must be supplied in the diet.

Phenylketonuria (PKU): An autosomal recessive disorder of amino acid metabolism that results in intellectual disability if untreated.

Galactosemia: A heritable trait associated with the inability to metabolize the sugar galactose. If it is left untreated, high levels of galactose-1-phosphate accumulate, causing cataracts and intellectual disability.

Hemoglobin variants: Alpha and beta globins with variant amino acid sequences.

Thalassemias: Disorders associated with an imbalance in the production of alpha and beta globin.

Pharmacogenetics: A branch of genetics concerned with the identification of protein variants that underlie differences in the response to drugs.

Ecogenetics: A branch of genetics that studies genetic traits related to the response to environmental substances.

Mutation rate: The number of events that produce mutated alleles per locus per generation.

Trinucleotide repeats: A form of mutation associated with the expansion in copy number of a nucleotide triplet in or near a gene.

Mutagens: Physical or chemical agents that cause mutations.

Tautomeric shift: A reversible structural change in a molecule brought about by a shift in the location of a hydrogen atom.

Radiation: The process by which electromagnetic energy travels through space or a medium such as air.

Background radiation: Radiation in the environment that contributes to radiation exposure.

Rem: The unit of radiation exposure used to measure radiation damage in humans. It is the amount of ionizing radiation that has the same effect as a standard dose of x-rays.

Millirem: A rem is a measure of radiation dose equal to 1000 millirems.

Base analogs: A purine or pyrimidine that differs in chemical structure from those normally found in DNA and RNA.

Nucleotide substitutions: Mutations that involve replacement of one or more nucleotides in a DNA molecule with other nucleotides.

Frameshift mutations: Mutational events in which a number of bases (other than multiples of three) are added to or removed from DNA, causing a shift in the codon reading frame.

Missense mutations: Mutations that cause the substitution of one amino acid for another in a protein.

Sense mutations: Mutations that change a termination codon into one that codes for an amino acid. Such mutations produce elongated proteins.

Nonsense mutations: Mutations that change an amino acid specifying a codon to one of the three termination codons.

Allelic expansion: Increase in gene size caused by an increase in the number of trinucleotide repeat sequences.

Epigenetics: The study of chemical modifications of chromosomal DNA (such as methylation of bases) and/or associated histone proteins that change the pattern of gene expression without affecting the nucleotide sequence of the DNA.

Epigentic trait: Phenotype that is produced by epigenetic changes to DNA.

Epigenome: The epigenetic state of a cell.

Promoter: Regulatory region located at the beginning of a gene.

Methylation: Addition of a methyl group to a DNA base or a protein.

Genetic imprinting: Selective expression of either the maternal or paternal copy of a gene.