Bio Chp17
Terms
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- Point Mutations
- A change in a gene at a single nucleotide pair.
- Poly-A Tail
- The modified end of the 3' end of the mRNA consists of the addition of 50-250 adenine nucleotides.
- Polyribosomes
- An aggregation of several ribosomes attached to one mRNA molecule found in both prokaryotic/eukaryotic cells that allows cell to make many copies of a polypeptide quickly.
- Primary transcript
- Initial RNA transcript also known as pre-mRNA transcribed from a protein-coding gene.
- Promoter
- Specific nucleotide sequence in DNA that binds RNA polymerase and indicates where to start transcribing RNA
- Ribosomes
- cell organelle constructed in the nucleolus that functions in protein synthesis. composed of 2 subunits: rRNA and
- RNA processing
- Modification of RNA before it leaves the nucleus, transcription of a protein-coding eukaryotic gene that results in pre-mRNA
- spliceosome
- complex assembly that interacts with the ends of an RNA intron in splicing RNA to release introns while joining adjacent exons
- signal peptide
- stretch of amino acids that targets a protein to a specific destination in a eukaryotic cell
- signal recognition particle(SRP)
- protein-RNA complex that recognizes a signal peptide as it emerges from the ribosome.
- Template strand
- One of 2 DNA strands that serves as a template for ordering the sequence of nucleotides in an RNA transcript
- Transfer RNA
- RNA molecule that functions as an interpreter between the protein and nucleic acid by taking an amino acid and recognizing the appropriate condons in the mRNA
- Reading frame
- the way mRNA nucleotides are arranged in codons by the mRNA-translating machinery
- Ribosomal RNA
- The most abundant type of RNA, component of ribosomes, coordinates sequential coupling of tRNA molecules to mRNA codons
- Ribozymes
- enzyme-like RNA molecules that catalyze reactions during RNA splicing
- RNA polymerase
- enzyme that pries 2 strands of DNA apart and hooks RNA nucleotides to the DNA template by base-pairing. It can only assemble in the 5' - 3' direction and is able to start chain without primer.
- RNA splicing
- removal of noncoding introns of the RNA molecule after initial synthesis
- TATA
- promoter DNA sequence crucial to the transcription initation complex, about 25 nucleotides upstream from transcriptional start point
- Terminator
- special sequence of nucleotides in DNA that mark the end of a gene, signaling RNA polymerase to release newly made RNA molecule and departs from the gene
- Transcription
- synthesis of RNA on a DNA template
- transcription factors
- regulatory protein molecule that binds to DNA and stimulates transcription of specific genes
- Transcription initiation complex
- completed assembly of transcription factors and RNA polymerase bound to the promoter
- Transcription unit
- stretch of DNA that is transcribed to an RNA molecule
- Translation
- synthesis of a polypeptide using genetic information encoded in an mRNA molecule. Cell must translate the base sequence of polypeptide.
- Triplet Code
- 3 nucleotides that specify amino acids for polypeptide chain
- Wobble
- violation of the base-pairing rules on the 3rd nucleotide on the 5' end of a tRNA molecule that can form H bonds with more than one kind of base on the 3rd nucleotide on the 3' end of a codon
- 5' cap
- 5' end of a pre-mRNA molecule modified by addition of a cap of guanine nucleotide
- A site
- One of a ribosome's 3 binding sites for tRNA during translation, holds the tRNA carrying the next amino acid to be added to the polypeptide chain
- Alternative RNA splicing
- type of 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
- Aminoacyl-tRNA synthetase
- enzyme that joins each amino acid to correct tRNA. active site only fits a specific combination of amino acid and tRNA
- anticodon
- specialized base triplet at one end of a tRNA molecule that recognizes a particular complementary codon on an mRNA molecule
- base-pair substitution
- type of point mutation; the replacement of one nucleotide and its partner in the complementary DNA strand by another pair of nucleotides
- Codon
- mRNA base triplets written in 5' to 3' direction, each specifying which of 20 amino acids will be incorporated at position along the polypeptide
- domains
- independently folding part of a protein
- frameshift mutation
- mutation occuring when the number of nucleotides deleted/inserted is not a multiple of 3, resulting in improper grouping of the following nucleotides into codons
- E site
- one of ribosome's 3 binding sites for tRNA during translation. discharged tRNAs leave the ribosome through this site
- Exons
- coding region of eukaryotic gene, can only be expressed when introns are removed
- introns
- noncoding, intervening sequence of nucleotides between coding regions
- mRNA
- type of RNA synthesized from DNA that attaches to ribosomes in the cytoplasm and specifies the primary structure of protein
- missense
- common type of mutation, base-pair substitution in which new codon makes sense in that it still codes for an amino acid
- mutagens
- chemical/physical agent that interacts with DNA to cause a mutation, some interfere with DNA replication by inserting themselves
- Mutations
- change in DNA of a gene that ultimately creates genetic diversity
- nonsense mutation
- mutation that changes an amino acid codon to one of the 3 stop codons resulting in shorter nonfunctional protein
- one gene-one polypeptide hypothesis
- premise that a gene is a segment of DNA that codes for one polypeptide
- P site
- one of a ribosome's 3 binding sites for tRNA, holds the tRNA carrying the growing polypeptide chain