Term
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Definition
| The process by which DNA directs protein synthesis, includes two stages: transcription and translation |
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Term
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Definition
Each gene codes for a specific polypeptides
Proteins are often composed of several polypeptides, each with its own gene |
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Term
Transcription (def)
Translation (def) |
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Definition
- Transcription: is the synthesis of RNA under the direction of DNA, produces mRNA (messenger)
- Translations: the synthesis of a polypeptide which occurs under the direction of mRNA at the ribosomes |
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Term
RNA processing (def)
Primary Transcript (def) |
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Definition
- Eukaryotic RNA transcripts are modified to yield finished mRNA, both ends of the primary usually altered, some inner parts are cut out or spliced
- A primary transcript is the initial RNA transcript from any gene |
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Term
Codon (def)
Triplet code (def) |
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Definition
- Sequence of three nucleotide bases that code for a specific amino acid, read in the 5' to 3' direction
- Nonoverlapping three nucleotide words |
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Term
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Definition
- 64 codons were deciphered by the mid 60s
- 61 code for amino acids; 3 triplets are stop signals to end translation
- The genetic code is redundant but not ambiguous, each codon specifies only one amino acid |
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Term
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Definition
- Catalyzes RNA synthesis
- Pries apart DNA strands and hooks together RNA nucleotides |
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Term
Promoter (def)
Terminator (def)
Transcription Unit (def) |
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Definition
Promoter - DNA sequence where RNA polymerase attaches
Terminator - in bacteria, sequence signaling the end of the transcription
Transcription Unit - stretch of DNA that is transcribed |
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Term
| Three stages of transcription |
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Definition
Initiation
Elongations
Termination |
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Term
Transcription factors
Transcription initiation complex |
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Definition
Factors - mediate the binding of RNA polymerase and initiate transcription
Complex - The completed assembly of transcription factors and RNA polymerase II bound to a promoter |
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Term
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Definition
| A promoter that is crucial in forming the initiation complex in eukaryotes |
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Term
| Mechanisms of Termination, bacteria and eukaryotes |
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Definition
Bacteria: transcription stops at the end of the terminator
Eukaryotes: polymerase continues transcription after the pre-mRNA is cleaved from the RNA chain; the polymerase eventually falls off the DNA |
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Term
5'cap
poly-A tail
Functions? |
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Definition
- 5' cap is a modified nucleotide put on the 5' end of the mRNA
- poly-A cap is placed on the 3' end of the mRNA
Functions - facilitate transport, protect mRNA from hydrolytic enzymes, help ribosomes attach to the 5' end |
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Term
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Definition
Introns - long noncoding stretches of nucleotides that lie between coding regions
Exons - other regions that are eventually expressed, usually translated into amino acid sequences |
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Term
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Definition
- Catalytic RNA molecules that function as enzymes and can splice RNA
- The discovery of ribozymes rendered obsolete the belief that all biological catalysts were proteins |
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Term
| The Functional and Evolutionary Importance of Introns |
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Definition
- Some genes can encode more than one kind of polypeptide, depending on which segments are treated as exons during RNA splicing
- Such variations are called alternative RNA splicing
- Because of alternative splicing, the number of different proteins an organism can produce is much greater than its number of genes |
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Term
| Aminoacyl-tRNA synthetase |
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Definition
| Makes/finds a correct match between a tRNA and an amino acid |
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Term
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Definition
| Flexible pairing at the third base of a codon is called wobble and allows some tRNAs to bind more than one codon |
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Term
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Definition
E - exit site, where discharged tRNA leaves the ribosome
P - holds the tRNA that carries the growing polypeptide chain
A - hold the tRNA that carries the next amino acid to be added to the chain |
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Term
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Definition
Multiple ribsomes attached to the same mRNA strand, translating the polypeptide simultaneously
- Allows cell to quickly make many copies |
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Term
Missense mutation
Nonsense mutation |
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Definition
Mis - still code for an amino acid, but not necessarily the right amino acid
Non - changes codon into stop codon, nearly always leading to a nonfunctional protein |
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Term
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Definition
Mutation that alters the reading frame of the mRNA
Insertions and deletions are the cause |
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