AP Biology Campbell Chapter 17

  1. 5' cap
    A modified form of guanine nucleotide added onto the nucleotide at the 5' end of a pre-mRNA molecule.
  2. A site
    One of a ribosome’s three binding sites for tRNA during translation. The A site holds the tRNA carrying the next amino acid to be added to the polypeptide chain. (A stands for aminoacyl tRNA.)
  3. alternative RNA splicing
    A type of eukaryotic gene regulation at the RNA-processing level in which different mRNA molecules are produced from the same primary transcript, depending on which RNA segments are treated as exons and which as introns.
  4. amino acid
    An organic molecule possessing both carboxyl and amino groups. Amino acids serve as the monomers of polypeptides.
  5. aminoacyl-tRNA synthetase
    An enzyme that joins each amino acid to the appropriate tRNA.
  6. anticodon
    (an´-ti-ko´-don) A nucleotide triplet at one end of a tRNA molecule that recognizes a particular complementary codon on an mRNA molecule.
  7. base-pair substitution
    A type of point mutation; the replacement of one nucleotide and its partner in the complementary DNA strand by another pair of nucleotides.
  8. chaperonin
    (shap'-er-o'-nin) A protein molecule that assists in the proper folding of other proteins.
  9. codon
    (ko´-don) A three-nucleotide sequence of DNA or mRNA that specifies a particular amino acid or termination signal; the basic unit of the genetic code.
  10. domain
    (1) A taxonomic category above the kingdom level. The three domains are Archaea, Bacteria, and Eukarya. (2) An independently folding part of a protein.
  11. E site
    One of a ribosome’s three binding sites for tRNA during translation. The E site is the place where discharged tRNAs leave the ribosome. (E stands for exit.)
  12. endomembrane system
    The collection of membranes inside and around a eukaryotic cell, related either through direct physical contact or by the transfer of membranous vesicles; includes the smooth and rough endoplasmic reticulum, the Golgi apparatus, lysosomes, and vacuoles.
  13. exon
    A sequence within a primary transcript that remains in the RNA after RNA processing; also refers to the region of DNA from which this sequence was transcribed.
  14. frameshift mutation
    A mutation occurring when the number of nucleotides inserted or deleted is not a multiple of three, resulting in the improper grouping of the subsequent nucleotides into codons.
  15. gene expression
    The process by which DNA directs the synthesis of proteins or, in some cases, just RNAs.
  16. insertion
    A mutation involving the addition of one or more nucleotide pairs to a gene.
  17. intron
    (in´-tron) A noncoding, intervening sequence within a primary transcript that is removed from the transcript during RNA processing; also refers to the region of DNA from which this sequence was transcribed.
  18. messenger RNA (mRNA)
    A type of RNA, synthesized using a DNA template, that attaches to ribosomes in the cytoplasm and specifies the primary structure of a protein.
  19. missense mutation
    A base-pair substitution that results in a codon that codes for a different amino acid.
  20. mutagen
    (myu´-tuh-jen) A chemical or physical agent that interacts with DNA and causes a mutation.
  21. mutation
    (myu-ta´-shun) A change in the nucleotide sequence of an organism’s DNA, ultimately creating genetic diversity. Mutations also can occur in the DNA or RNA of a virus.
  22. nonsense mutation
    A mutation that changes an amino acid codon to one of the three stop codons, resulting in a shorter and usually nonfunctional protein.
  23. P site
    One of a ribosome’s three binding sites for tRNA during translation. The P site holds the tRNA carrying the growing polypeptide chain. (P stands for peptidyl tRNA.)
  24. point mutation
    A change in a gene at a single nucleotide pair
  25. poly-A tail
    A sequence of 50 to 250 adenine nucleotides added onto the 3' end of a pre-mRNA molecule.
  26. polyribosome (polysome)
    (pol´-e-ri´-bo-som´) A group of several ribosomes attached to, and translating, the same messenger RNA molecule.
  27. primary transcript
    An initial RNA transcript; also called pre-mRNA when transcribed from a protein-coding gene.
  28. promoter
    A specific nucleotide sequence in DNA that binds RNA polymerase, positioning it to start transcribing RNA at the appropriate place.
  29. radiation
    The emission of electromagnetic waves by all objects warmer than absolute zero.
  30. reading frame
    On an mRNA, the triplet grouping of ribonucleotides used by the translation machinery during polypeptide synthesis.
  31. ribosomal RNA (rRNA)
    (ri´-buh-so´-mul) The most abundant type of RNA, which together with proteins makes up ribosomes.
  32. ribosome
    (ri'-buh-som') A complex of rRNA and protein molecules that functions as a site of protein synthesis in the cytoplasm; consists of a large and a small subunit. In eukaryotic cells, each subunit is assembled in the nucleolus. See also nucleolus.
  33. ribozyme
    (ri´-bo-zim) An RNA molecule that functions as an enzyme, catalyzing reactions during RNA splicing.
  34. RNA polymerase
    An enzyme that links ribonucleotides into a growing RNA chain during transcription.
  35. RNA processing
    Modification of RNA transcripts, including splicing out of introns, joining together of exons, and alteration of the 5' and 3' ends.
  36. RNA splicing
    After synthesis of a eukaryotic primary RNA transcript, the removal of portions (introns) of the transcript that will not be included in the mRNA.
  37. signal peptide
    A sequence of about 20 amino acids at or near the leading (amino) end of a polypeptide that targets it to the endoplasmic reticulum or other organelles in a eukaryotic cell.
  38. signal-recognition particle (SRP)
    A protein-RNA complex that recognizes a signal peptide as it emerges from a ribosome and helps direct the ribosome to the endoplasmic reticulum (ER) by binding to a receptor protein on the ER.
  39. spliceosome
    (spli´-se-o-som) A large complex made up of proteins and RNA molecules that splices RNA by interacting with the ends of an RNA intron, releasing the intron and joining the two adjacent exons.
  40. TATA box
    A DNA sequence in eukaryotic promoters crucial in forming the transcription initiation complex.
  41. template strand
    The DNA strand that provides the pattern, or template, for ordering the sequence of nucleotides in an RNA transcript.
  42. terminator
    In bacteria, a sequence of nucleotides in DNA that marks the end of a gene and signals RNA polymerase to release the newly made RNA molecule and detach from the DNA.
  43. transcription
    The synthesis of RNA using a DNA template.
  44. transcription factor
    A regulatory protein that binds to DNA and affects transcription of specific genes.
  45. transcription initiation complex
    The completed assembly of transcription factors and RNA polymerase bound to a promoter.
  46. transcription unit
    A region of DNA that is transcribed into an RNA molecule.
  47. transfer RNA (tRNA)
    An RNA molecule that functions as an interpreter between nucleic acid and protein language by picking up specific amino acids and recognizing the appropriate codons in the mRNA.
  48. translation
    The synthesis of a polypeptide using the genetic information encoded in an mRNA molecule. There is a change of “language” from nucleotides to amino acids.
  49. triplet code
    A set of three-nucleotide-long words that specify the amino acids for polypeptide chains.
  50. wobble
    Flexibility in the base-pairing rules in which the nucleotide at the 5' end of a tRNA anticodon can form hydrogen bonds with more than one kind of base in the third position (3' end) of a codon.
Card Set
AP Biology Campbell Chapter 17
key terms for chapter 17