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51 Cards in this Set
- Front
- Back
one gene-one polypeptide hypothesis
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discovered by Beadle and Tatum
-not all proteins are enzymes - proteins are contructed from two ore more different polypeptide chains -each polypeptide is specified by its own gene |
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transcription
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synthesis of RNA under the direction of DNA
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mRNA
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messenger RNA
-carries a genetic message from DNA to the protein to be synthesized by the machinery of the cell |
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translation
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synthesis of a polypeptide under the direction of mRNA
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where does translation occur?
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in the ribosomes
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synthesis in prokaryotes
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transcription and translation occur simulaneously
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synthesis eukaryotes
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nuclear envelopeps separates transcription from translation
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primary transcript
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initial RNA transcript
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triplet code
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the genetic insructions for polypeptide chain
- series of three nucleotides |
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template strand
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- for each gene only one of the two DNA strands is transcribed
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codons
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mRNA base triplets that specify for an amino acid
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AUG
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methionine (Met)
initiation codon that signals the protein-synthesizing machine to begin translating the mRNA at the location |
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termination codons
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signal the end of translation
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redundancy but no ambiguity
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-two codons may specify one amino acid
-neither of any two codons specifies any other amino acid |
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reading frame
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reading the symbols in the correct sequence and groupings
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RNA polymerase
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pries the two strands of DNA apart and hooks together the RNA nucleotides as they base-[air along the DNA template
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direction that RNA molecule elongates?
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5'--> 3'
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RNA polymerase II
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type of RNA polymerase used for mRNA synthesis
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three stages of transcription
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initiation, elongation, and termination of the RNA chain
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promoter
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region of DNA where RNA polymerase attaches and initiates transcription
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what are two functions of the promoter?
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-determines where transcription starts.
- determines whihch of the two strands of the DNA helix is used as the template. |
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other (nontemplate strand)
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provides the instructions for making a new template strand when the DNA replicates
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transcription factors
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collection of proteins in Eukaryotes which mediate the binding of RNA polymerase and the initiation of transcription
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transcription initiation complex
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completed assembly of transcription factors and RNA polymerase bound to the promoter
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TATA box
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promoter DNA sequence
- crucial in forming the iniation complex |
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RNA splicing
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cut and paste job
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introns
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noncoding segments of nucleic acid that lie between coding regions
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exons
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regions of nucleic acd that are eventually expressed
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snRPs
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( small nuclear ribonucleic proteins)
signal RNA splicing -located in the nucleus -composed or RNA and protein molecules - |
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snRNA
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(small nuclea RNA)
the RNA in a snRNP particle - 150 nucleotides long |
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spliceosome
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an assembly of several additional proteins ( almost as big a ribosome)
- cuts at specidic points to release the intron, then immediately joins together the two exons that flanked the intron |
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ribozymes
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RNA molecules that function as enzymes
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structural domain
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- structure that is self-stabilizing and often folds independently of the rest of the protein chain.
- classified into "folds |
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how are introns related to variety?
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introns increase the opportunity for crossing over between two alleles of a gene, raising the probability that a crossover will switch one version of an exon for another version found on the homologous chromosome
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tRNA
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( transfer RNA)
transfers amino acids from the cytoplasm's amino acid pool to a ribosome |
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anticodon
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nucleic triplet which binds according to base-pair rules to a complementary codon on mRNA
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wobble
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relaxation of base pair rules
ex: the bae U of a tRNA anticodon can pair with either Aor G in the third posistion of an mRNA codon |
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aminoacyl-tRNA
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enzyme that joins each amino acid to the correct tRNA
-20 in each cell |
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number of amino acids in a cell
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20
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rRNA
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(ribosomal RNA)
type of RNA that is the central component of the ribosome |
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P site
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binding site for tRNA
- holds the tRNA carrying the growing polypeptide chain |
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A site
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binding site for tRNA
- hold the tRNA carrying the 2nd anmino aicd to be added to the chain |
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E site
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( exit site)
-site where discharged tRNAs leave the ribosome |
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initiation
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brings together mRNA, a tRNA bearing the first amino acid of the polypeptide, and the two subunits of a ribosome
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mutations
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changes in the genetic information of a vell
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base-pair substitution
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replaces one nucelotide and it complementary partner with another pair of nucleotides
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missense mutation
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substitution that results in an incorrectly coded amino acid
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Nonsense mutations
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occur when the point mutation changes an amino acid codon into a stop codon
-halts translation early |
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frameshift mutatitions
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-mutations that alter the reading frame
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SRP
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signal-recognition particle
-attaches the ribosome to a receptor protein |
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signal peptide
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begins polypeptide chain destined to be for secretion
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