chapter 17 terms 2
Terms
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- one gene- one polypeptide hypothesis
- the premise that a gene is a segment of DNA that codes for one polypeptide
- transcription
- the synthesis of RNA or DNA template
- messenger RNA (mRNA)
- a type of RNA synthesized from DNA that attaches to ribosomes in the cytoplasm and specifies the primar structure of a protein
- translation
- the synthesis of a polypeptide using the genetic info encoded in an mRNA molecule. There is a change of "language" from nucleotides to amino acids
- RNA processing
- modification of RNA before it leaves the nucleus, a process unique in eukaryotes
- primary transcript
- an initial RNA transcript also called pre-mRNA
- triplet code
- a set of 3 nucleotide long words that specify the amino acids for polypeptide chain
- template strand
- the DNA strand that provides the template for ordering the sequence of nucleotides in an RNA transcript
- reading frame
- the way a cell's mRNA-translating machinary groups the mRNA nucleotides into codons
- RNA polymerase
- an enzyme that links together the growing chain of ribonucleotides during transcription
- promoter
- a specific nucleotide sequence in DNA that binds RNA polymerarse and indicates where to start transcribing RNA
- terminator
- a special sequence of nucleotides in DNA that marks the end of a gene. It signals RNA polymerase to release the newly made RNA molecule, which then departs from the gene
- transcription unit
- the stretch of DNA that is transcribed into an RNA molecule
- transcription factor
- a regulatory protein that binds to DNA and stimulates transcriptioin of specific genes
- transcription inhbition complex
- the completed assembly of transcription factors and RNA polymerase bound to the promoter
- TATA box
- a promoter DNA sequence crucial in forming the transcription initiation complex
- 5' cap
- the 5' end of a pre-mRNA molecule modified by the addition of a cap of guanine nucleotide
- transfer RNA (tRNA)
- an RNA molecule that functions as an interpreter between nucleic acid and protein languange by picking up specific amino acids and recognizing the appropraite codons in the mRNA
- poly(A)tail
- the modified end of the 3' end of an mRNA molecule consisting of the addition of some 50 to 250 adenine nucleotides
- RNA splicing
- the removal of noncoding protions (introns) of the RNA molecule after initial synthesis
- introns
- a noncoding, intervening sequence within a eukaryotic gene
- exon
- a coding region of a eukaryotic gene that are expressed, and speparted from each other by introns
- splicesome
- a complex assembly that interacts with the ends of an RNA intron in splicing RNA, releasing the intron and joining the two adjacent exons
- ribozyomes
- an enzymatic RNA molecule that catalyzes reations during RNA splicing
- alternative RNA splicing
- a type of reglation at the RNA processing level where different mRNA molecules are produced from the same primary transcript depending on which RNA segments are treated as exons and which as introns
- domains
- proteins modular architecture consisting of discrete structural and functional regions
- anticodon
- a specialized base triplet at 1 end of a tRNA molecules that reconizes a particular complementary codon on an mRNA molecule
- wobble
- a violation of the base pairing rules in that the 3rd nucleotide (5' end) of a tRNA anticodon can form hydrogen bonds with more than one kind of base in the 3rd position (3' end) of a codon
- aminoacl tRNA synthetase
- an enzyme that joins each amino acid to the correct tRNA
- ribosomal RNA (rRNA)
- the most abundant type of RNA, which together with proteins, forms the structure of ribosomes. ribosomes coordinate the sequential coupling of tRNA molecules to mRNA codons
- A site
- 1 of 3 binding sites for tRNA during translation, it holds the tRNA carrying the next amino acid to be added to the polypeptide chain; stands for aminoacyl-tRNA site
- P site
- 1 of 3 binding sites for tRNA during translation, it holdes the tRNA carrying the growing polypeptide chain; stands for peptidyl tRNA site
- E site
- 1 of 3 binding sites for tRNA during translation, it is the place where discharaged tRNAs leave the ribosome; exit site
- polyribosoome
- an aggregation of several ribosomes attached to 1 messenger RNA molecule
- single peptide
- marks the polypeptides of proteins destined for the endomembrane system or for secretion
- signal recognition particle (SRP)
- a protein RNA complex that recognizes a signal peptide as it emerges from the ribosome
- point mutations
- a change in a gene at a single nucleotide pair
- base pair substitution
- a point mutation; the replacement of 1 nucleotide and its partner in the complementary DNA strand by another pair of nucleotides
- missense mutations
- the most common type of mutation, a base pair substitution where the new codon makes sense in that it still codes for an amino acid
- nonsense mutations
- a mutation that changes an amino acid codon to 1 of the 3 stop codons, resulting in a shorter and usually nonfunctional protein
- insertion
- a mutation involving the addition of 1 or more nucleotide pairs to a gene
- deletion
- a mutational loss of1 or more nucleotide pairs from a gene
- frameshift mutation
- a mutation occurring when the number of nucleotides inserted or deleted its not a multiple of 3, resulting in the improer grouping of the following nucleotides into codons
- mutagens
- a chemical or physical agent that interacts with DNA and causes a mutation