Lecture 12 Flashcards
Unidirectional
Information can only go in one direction
Gene
A region of DNA that is transcribed and has a function in the cell
Promoter
Site of RNA polymerase assembly, DNA sequence that determines start of gene, no promoter means no gene
TATA Box
AT rich sequence found 10 base pairs before transcription start
Transcription Factors
Proteins that recognize and bind the TATA box, can read DNA, recruits RNA polymerase because RNA pol can’t identify promoter on its own
Transcription
DNA to mRNA
Template Strand
Used in transcription, runs 3’ to 5’ away from promoter
Coding Strand
Complementary and antiparallel to template, runs 5’ to 3’ away from promoter, not used in transcription
Transcript
mRNA product
RNA Polymerase
Enzyme of transcription, part of a transcription initiation complex that assembles at the promoter, can open DNA into a transcription bubble
UTR
Untranslated region, space on RNA either before translation start or after translation stop
Elongation
Occurs where RNA polymerase add nucleotides 5’ to 3’ and transcript is released out of complex
Post-transcriptional Processing
Eukaryotes only, occurs in nucleus, increase stability of transcript
meG Cap
Methylguanosine cap, modified base, forms a 5’ to 5’ linkage with eukaryotic mRNA to hide 5’ end from exonuclease digestion
PolyA Tail
Added to 3’ end of eukaryotic mRNA, delays exonuclease digestion and aids in translation initiation.
RNA Splicing
Removal of intervening sequences from coding region (introns)
Introns
Non-amino acid coding regions which contain intervening sequences found in a eukaryotes gene’s DNA but not in the mature mRNA
Exons
Amino acid coding regions which contain expressed sequences found in both a eukaryotes gene’s DNA and in the mature mRNA
Spliceosome
Complex of snRNPs, enzyme of splicing
snRNPs
Protein/RNA complexes (quaternary structure) which recognize sequences at intron/exon boundaries
Alternative Splicing
Mixing and matching of exons, makes similar but not identical proteins from same gene
Translation
RNA to Protein
Codon
3 nucleotides associated with an amino acid
tRNA
Transfer RNA, functional RNA, amino acid binding region and mRNA base pairing region (anticodon), carries appropriate amino acid to ribosome
Anticodon
Antiparallel and complementary to mRNA codon
Aminoacyl tRNA Synthetase
Enzyme that pairs correct amino acid based on anticodon sequence, covalently links amino acid to tRNA, energy from ATP hydrolysis
Ribosomes
Catalyze peptide bonds
Large Ribosomal Subunit
Contains rRNA and catalytic site
Small Ribosomal Subunit
Contains rRNA and recognizes and binds RBS (reads mRNA)
RBS
Ribosomal binding site, prokaryote only, sequence in mRNA that is recognized by base pairing with rRNA in small ribosomal subunit
Formyl-methionine
Modified amino acid, unique to prokaryotes, first amino acid of protein synthesis (found on amino terminal)
Bind
Charged tRNA approaches A site and binds to the mRNA (anticodon-codon base pairing)
Bond
Peptide bond forms between amino acid chain attached to tRNA 1 and amino acid on tRNA 2, peptide chain transfers to tRNA 2
Shift
Ribosome shifts down that mRNA (towards 3’ end) in a 1 codon step
Mutagens
Mutation causing factors
Mutations
Changes to sequence in DNA
Base-pair Substitution
Mutation at the DNA level, replacement of one nucleotide and its partner with another pair
Silent Mutation
Mutation at the protein level, no change in primary amino acid sequence due to redundancy in genetic code
Missense Mutation
Mutation at the protein level, encodes the wrong amino acid, MAY affect protein function
Nonsense Mutation
Mutation at the protein level, premature stop codon, shortened protein, may affect protein structure
Frameshift Mutation
Mutation at the protein level, single base pair addition or deletion that changes the reading frame of a protein
Spontaneous Mutation
Error in copying of DNA sequence
Induced Mutation
Exposure to mutagens
