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19 Cards in this Set
- Front
- Back
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gene |
-hereditary unit (DNA sequence that encodes a protein) |
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coding sequence |
-stipulates the amino acid sequence |
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termination sequence |
-marks the end of the gene |
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most genes encode ______ |
-proteins: structural (cell shape), enzymes (metabolism), receptors (interxn with the environment), regulatory (ctrl gene expression) -requires transcription and translation |
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some genes encode ______ |
-RNA molecules: rRNA, tRNA, snRNA, snoRNA, miRNA -requires transcription and sometimes RNA processing |
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central dogma of genetics |
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promoters |
-regulatory DNA sequence at upstream (5') region of gene -enables response to changes in the envmt (internal and external) -contains regulatory sequences that define the beginning of the gene -transcription machinery binds to regulation sequences so RNA can be synthesized by RNA polymerases -only one strand of the DNA is read but genes can be located on either strand |
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prokaryotic promoters |
-TATAAT: (-10 region) "Pribnow box" -TTGACA: (-35 region) |
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eukaryotic promoters |
-TATAAAA: (-30 region) "TATA box" -GGCCAATCT: (-80 region) "CAAT box" -additional regulatory sequences (binding of specific proteins) -typical eukaryotic promoter = 2 kb |
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coding region |
-spells out sequence of amino acids -based on a codon triplet -3 nucleotides = amino acid |
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start codon |
-AUG (ATG in DNA) -codes for methionine (Met or M) |
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codon table |
-universal (but doesn't apply to EVERY organism) -degenerate/redundant (4 x 4 x 4 = 64 potential triplets, but only 20 amino acids) -wobble hypothesis |
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exons and introns |
-exons: expressed sequences (code amino acids)
-introns: interspersed sequences (do not encode amino acids; transcribed but not translated) -eukaryotic mRNA |
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prokaryotic mRNA |
-don't typically contain introns -polycistronic: multiple genes represented in one mRNA; transcriber from one promoter -no nucleus allows mRNA to be directly translated |
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termination |
-coding sequence ends with a STOP codon: UGA UAA UAG -transcription ends beyond stop codon -stop codon isn't for transcription, it's for translation |
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UTRs |
-untranslated regions (before start codon and after stop codon) -affect: stability (degrades slower, exists longer in cell), nuclear export, subcellular localization, rate of degradation |
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eukaryotic genomes |
-genes encode a single protein or single mRNA -each gene has its own regulatory sequence and is expressed independently -one gene = one product -genes do not overlap -possible to get different mRNAs from a single gene depending on which exons are spliced together: splice variants -sometimes splicing differences between males and females |
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prokaryotic vs eukaryotic gene structure |
-prokaryotic genes can be stacked together (one promoter with multiple genes) -genes are in tandem, functions are related, genes are expressed together -e.g. operons in prokaryotes: genes that encode enzymes involved in a common function are linked |
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viral gene structure |
-ultimate efficiency -some viral DNA sequences have overlapping genes -nucleotide can be included in more than one codon -red from different frames |
