RNA

• One way body can limit spread of virus

  - shut off process of transcription and translation
• Interferon


  - help limit spread of virus

  - induces production of RNaseI
• RNAse I


  - cleaves RNA

  - reduces the ability of virus replication
• Central dogma


  DNA -(1)-> RNA -(2)-> Protein

  - DNAreplicatesitself

  - (1) = transcription

  - (2) = translation

  - reverse of 1 = reverse transctiption
• Gene


  - unit of DNA

  - encodes a specific protein or RNA molecule

  - expressed through transcription and translation
• Messenger RNA is synthesized from ___________

  5' --> 3'

  - complementary and antiparallel to DNA template strand
• Ribosome translates the mRNA from _________

  5' --> 3'

  - synthesizes the protein from amino (N) to carboxy terminus (C)
• Types of RNA (main)

  - mRNA (most abundant)

  - tRNA

  - rRNA
• mRNA


  - messenger RNA

  - specifies amino acid sequence

  - transcribed from template DNA

  - made by RNA polymerase

  - in nucleus

  - undergo post-transcriptional modification

  - only RNA that has info to make proteins

  - read in codons
• Monocistronic


  - mRNA in eukaryotes

  - each mRNA only translates to one protein product
• Polycistronic


  - mRNA in prokaryotes

  - starting at different parts of mRNA = dif protein

  - prokaryotes can also have monocistronic mRNA
• tRNA


  - transfer RNA

  - converts nucleotide into amino acids

  - made of a folded RNA strand

  - 3 nucleotide anti-codon

  - amino acids are connected to a specific tRNA

  - in cytoplasm

  - second most abundant form of RNA
• Anticodon


  - recognizes and pairs with appropriate codon

  - happen in ribosome
• Charged tRNA


  - tRNA is attached to amino acid

  - aka activated tRN
• Amino t-RNA synthetase


  - activates amino acid

  - requires 2 bonds from ATP = high energy = used to supply energy to create peptide bond

  - attaches amino acid to 3' end of tRNA = CCA
• rRNA


  - Ribosomal RNA

  - made in the nucleolus

  - integral part of ribosomal machinery

  - used to assemble protein in cytoplasm

  - many function as ribozymes

  - catalyze peptide bond formation

  - splices its own introns in the nucleus
• Ribozyme


  - enzyme made of RNA molecules instead of proteins
• Codon


  - 3 nucleotide sequence

  - translated into aa

  - 64 possible codons

  - always written from 5' --> 3'

  - unambiguous

  - universal across all species

  - recognized by anti-codon
• Unambiguous codon


  - one codon = one amino acid

  - each amino acid can be represented by multiple codons
• Anti-codon


  - complementary to codon

  - on a tRNA

  - allows tRNA to pair to mRNA codon

  - interaction = base pairing = antiparallel
• Start codon


  = methionine = AUG

  - every eukaryote protein starts with this
• Stop codon


  = UGA, UAA, UAG

  - no charged tRNA for this

  - triggers release of protein
• Types of mutations


  - silent

  - missense

  - nonsense

  - frameshift
• Silent mutations


  - point mutation in the wobble position

  - aka degenerate mutation

  - no effect on expression of aa

  - no adverse effect on polypeptide
• Wobble position


  - variable third base of codon

  - usually as long as first two bases right, third one doesn't matter to determine aa

  - also reason for genetic code being degenerate
• Degenerate genetic code


  - more than one codon can specify an aa

  - all aa except methionine and tryptophan are encoded by multiple codons
• Missense Mutation


  - due to a point mutation

  - is an expressed mutation

  - one amino acids is substituted for another
• Expressed mutation


  - affects the primary amino acid sequence

  - missense and nonsense
• Nonsense Mutation


  - due to a point mutation

  - expressed mutation

  - new codon = stop codon

  - aka truncation mutation
• Frameshift mutation


  - when a nucleotide is added or deleted

  - causes a shift in the reading frame

  - changes aa sequence or causes premature truncation

  - usually more serious than point mutation
• Reading frame


  - 3 nucleotides of a codon
• Transcription


  - occurs in cytoplasm = where the machinery is

  - creation of mRNA from DNA template

  - only copies one of two DNA strands
• DNA _______ leave the nucleus

  cannot
• Things required for transcription

  - helicase

  - topoisomerase

  - DNA-dependent RNA polymerase

  - promoter

  - RNA polymerase II

  - TATA box

  - Transcription factors
• Template strand


  - aka anti-sense strand

  - used to synthesize mRNA = antiparallel and complementary
• DNA-dependent RNA polymerase


  - in eukaryotes it is RNA polymerase II

  - binds to TATA box

  - does not require a primer like DNA polymerase III

  - travels from 3' --> 5'

  - transcribes from 5' --> 3'

  - does not proofread as it goes
• TATA box


  - promoter in DNA in eukaryotes

  - binds to RNA polymerase II

  - high concentration of thymine and adnenine bases
• Transcription factors


  - help RNA polymerase locate and bind to promoter
• Types of RNA polymerase in eukaryotes

  - RNA polymerase I

  - RNA polymerase II

  - RNA polymerase III
• RNA polymerase I


  - located in nucleolus

  - synthesizes rRNA