| A | B |
|---|
| 5’ cap | 5’ end of a pre-mRNA molecule modified by the addition of a cap of guanine nucleotide |
| A site | holds the tRNA carrying the next amino acid to be added to the polypeptide chain |
| alternative RNA splicing | different mRNA molecules are produced from the same primary transcript depending on which are exons and which are introns |
| aminoacyl-tRNA synthetase | enzyme that joins each amino acid to the correct tRNA |
| anticodon | base triplet at one end of a tRNA molecule that recognizes complementary codon on an mRNA molecule |
| base-pair substitution | replacement of one nucleotide and its partner in the complementary DNA strand by another pair of nucleotides |
| codon | three-nucleotide sequence of DNA or mRNA that specifies a particular amino acid |
| deletion | mutational loss of one or more nucleotide pairs from a gene |
| domain | independently folding part of a protein |
| E site | place where discharged tRNAs leave the ribosome |
| exon | coding (retained) region of a eukaryotic gene |
| frameshift mutation | occurring when the number of nucleotides inserted or deleted is not a multiple of three |
| insertion | addition of one or more nucleotide pairs to a gene |
| intron | noncoding |
| messenger RNA (mRNA) | attaches to ribosomes in the cytoplasm and specifies the primary structure of a protein. |
| missense mutation | base-pair substitution in which the new codon still codes for an amino acid |
| mutagen | chemical or physical agent that interacts with DNA and causes a mutation |
| mutation | rare change in the DNA of a gene |
| nonsense mutation | changes an amino acid codon to one of the three stop codons |
| one gene–one polypeptide hypothesis | gene is a segment of DNA that codes for one polypeptide |
| P site | holds the tRNA carrying the growing polypeptide chain |
| point mutation | change in a gene at a single nucleotide pair |
| poly-A tail | modified end of the 3’ end of an mRNA molecule |
| polyribosome (polysome) | aggregation of several ribosomes attached to one messenger RNA molecule. |
| primary transcript | initial RNA transcript; also called pre-mRNA when transcribed from a protein-coding gene |
| promoter | nucleotide sequence in DNA that binds RNA polymerase and indicates where to start transcribing RNA |
| reading frame | cell’s mRNA-translating machinery groups the mRNA nucleotides into codons |
| ribosomal RNA (rRNA) | with proteins forms the structure of ribosomes |
| ribosome | as the site of protein synthesis in the cytoplasm |
| ribozyme | enzymatic RNA molecule that catalyzes reactions during RNA splicing |
| RNA polymerase | links together the growing chain of ribonucleotides during transcription |
| RNA processing | Modification of RNA before it leaves the nucleus |
| RNA splicing | removal of noncoding portions (introns) of the RNA molecule after initial synthesis |
| signal peptide | amino acids on a polypeptide that targets the protein to a specific destination |
| signal-recognition particle (SRP) | protein-RNA complex that recognizes a signal peptide |
| spliceosome | assembly that in splicing RNA |
| TATA box | promoter DNA sequence crucial in forming the transcription initiation complex |
| template strand | provides the template for ordering the sequence of nucleotides in an RNA transcript |
| terminator | special sequence of nucleotides in DNA that marks the end of a gene |
| transcription | synthesis of RNA on a DNA template |
| transcription factor | regulatory protein that binds to DNA and stimulates transcription of specific genes |
| transcription initiation complex | assembly of transcription factors and RNA polymerase bound to the promoter |
| transcription unit | region of a DNA molecule that is transcribed into an RNA molecule |
| transfer RNA (tRNA) | interpreter between nucleic acid and protein language picks up specific amino acids |
| translation | synthesis of a polypeptide using the genetic information encoded in an mRNA |
| triplet code | three-nucleotide-long words that specify the amino acids for polypeptide chains |
| wobble | third nucleotide (5’ end) of a tRNA anticodon can form hydrogen bonds with more than one kind of base in the third position |
