Chapter 14.txt

  1. alternative splicing
    Event by which the same gene can specify two or more slightly different proteins. All exons in a pre-mRNA transcript of the gene are retained or some are removed and the rest spliced in various combinations for the mature transcript.
  2. amino acids
    A small organic compound with a carboxylic acid group, an amino group, and a characteristic side group (R); monomer of polypeptide chains.
  3. anticodon
    Series of three nucleotide bases in tRNA that can base-pair with mRNA codons.
  4. base sequence
    Linear order of nucleotides that compose a DNA or RNA strand.
  5. base-pair substitution
    Mutation in which one nucleotide is wrongly substituted for another during DNA replication.
  6. deletions
    Loss of a chromosome segment; often leads to genetic disorders. Also the loss of one or more nucleotide bases from a DNA molecule.
  7. exons
    A base sequence in eukaryotic DNA that is part or all of a protein-encoding gene; may or may not be excised from a pre-mRNA during transcript processing.
  8. gene mutations
    Small-scale change in the nucleotide sequence of a gene; can result in an altered protein product.
  9. genetic code
    Correspondence between triplets of nucleotides in DNA and mRNA, and specific sequences of amino acids in a polypeptide chain; near-universal language of protein synthesis; mitochondria and a few species have a few variant code words.
  10. insertions
    A mutation by which one or more bases are introduced into a DNA strand. Also a movable attachment of muscle to bone.
  11. introns
    One of the noncoding sequences in eukaryotic genes; it is excised from the pre-mRNA transcripts before translation.
  12. ionizing radiation
    Form of radiation with enough energy to eject electrons from atoms.
  13. messenger RNA
    mRNA. A single strand of ribonucleotides transcribed from DNA; the only type of RNA that carries proteinbuilding information to ribosomes.
  14. mutation rate
    Of a given gene locus, the probability that a spontaneous mutation will happen in a specified interval.
  15. nonionizing radiation
    Form of radiation that carries enough energy to boost electrons to higher energy levels but not enough to eject them from an atom.
  16. polysomes
    A series of ribosomes that are all translating the same mRNA molecule at the same time.
  17. promoter
    Short stretch of DNA to which RNA polymerase binds. Transcription then begins at the gene closest to the promoter.
  18. ribosomal RNA
    rRNA. A class of RNA that becomes complexed with proteins to form ribosomes; some catalyze assembly of polypeptide chains.
  19. ribosomes
    The site of polypeptide chain synthesis in all cells. An intact ribosome has two subunits of rRNA and proteins.
  20. RNA polymerase
    Enzyme that catalyzes transcription of DNA into RNA.
  21. transcription
    [L. trans, across, + scribere, to write] First stage of protein synthesis. An RNA strand is assembled from nucleotides using a gene region in DNA as a template.
  22. transfer RNA
    tRNA. One of a class of small RNA molecules that delivers amino acids to a ribosome. Its anticodon pairs with an mRNA codon during translation.
  23. translation
    Second stage of protein synthesis. At ribosomes, information encoded in an mRNA transcript guides the synthesis of a new polypeptide chain from amino acids.
  24. transposons
    Transposable element. A stretch of DNA that jumps spontaneously and randomly to a different location in the genome and may mutate a gene.
  25. uracil
    One of four nitrogencontaining bases in nucleotide monomers of RNA; also applies to a nucleotide with a uracil base component. Like thymine, uracil can base-pair with adenine.
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Chapter 14.txt
Chapter 14