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21 Cards in this Set
- Front
- Back
Gene Expression
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overall process by which DNA directs protein synthesis
(2 steps -- transcription and translation) |
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Transcription
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RNA copy made from DNA template
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Translation
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protein synthesized from RNA template
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Genetic information in all cells flows from:
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DNA --> RNA --> protein
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Triplet Code
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a series of nonoverlapping, three nucleotide words. (ex. ATG CCG TAC AGC TTA)
*these triplets code for all the amino acids |
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DNA to RNA
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*during transcription, the template strand provides the information for ordering the sequence of nucleotides in an RNA transcript
*mRNA transcript built 5' to 3' |
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RNA to protein
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*during translation, the mRNA base triplets, called codons, are read in the 5' to 3' direction
*each codon specifies the amino acid to be placed along a polypeptide *each codon specifies the addition of only ONE of the 20 amino acids |
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Promoter
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the dna sequence where RNA polymerase attaches
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Three Stages of Transcription
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Initiation
Elongation Termination |
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Transcription Factors
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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 II bound to a promoter
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TATA box
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a promotor
-- crucial in forming the initiation complex in eukaryotes |
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Introns
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noncoding stretches of nucleotides that lie between coding regions --> intervening sequences
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Exons
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noncoding stretches of nucleotides that lie between coding regions --> expressed
*usually translated into amino acid sequences |
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RNA splicing
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removes introns and joins exons, creating an mRNA molecule with a continuous coding sequence
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Transfer RNA (tRNA)
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a cell translates an mRNA message into protein
*each molecule of tRNA carries a specific amino acid on one end *each has an anti-codon on one end; the anticodon base pairs with a complementary codon on mRNA |
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Accurate translation requires two steps:
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first -- a correct match between a tRNA and its corresponding amino acid must be carried out by the enzyme aminoacyl-tRNA synthetase
second -- a correct match between the tRNA anticodon and the mRNA codon must take place |
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Ribosomes
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facilitate specific coupling of tRNA anticodons with mRNA codons in protein synthesis
*two ribosomal subunits include: proteins and rRNA |
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P Site
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holds the tRNA that carries the growing polypeptide chain
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A Site
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holds the tRNA that carries the next amino acid to be added to the chain
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E Site
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exit site, where discharged tRNAs leave the ribosome
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