Translation and Mutations

• What is translation?


  conversion of mRNA into protein; information contained in the mRNA molecules is decoded to form proteins

  ribosomes interact with 3 nucleotides (codon) on mRNA and tRNA charged with particular amino acids are delivered
• Each tRNA has an amino acid attached that is defined by tRNA ___________.

  anticodon
• When a ribosome "reads" the mRNA sequence (5' to 3') in translation, what happens?

  recruits tRNA for each codon
• What is the central dogma of molecular biology?

  DNA is transcibed into mRNA by RNA polymerase -> mRNA (contains info from DNA) is translated into protein by tRNA and mRNA. DNA is replicated by DNA polymerase
• How many codons and amino acids are in the genetic code? What are the start and stop codons?

  61 codons and 20 amino acids

  1 start codon (AUG)

  3 stop codons (UAA, UAG, and UGA)
• Are all organisms identical in terms of genetic code?

  yes
• How are the ribosomes in translation of bacteria?

  ribosomes are small with a large subunit
• What does initiation depend on in translation of bacteria?

  interaction between small ribosome subunits (16s RNA) and the Shine-dalagarno sequence (ribosome binding site) on mRNA molecule

  interaction helps align machinery to correct starting location
• What happens when ribosomes reach a stop codon?

  release factors cause the complex to come apart, releasing new protein for folding and modification
• Why is bacterial mRNA polycistronic?

  multiple shine-dalgarno sequences allow bacterial mRNA to code for more than one protein
• What happens to molecular chaperones are under 50 degree Celsius conditions?

  they bind to sequence which increases proteins
• What dos protein folding depend on?

  the number of interactions between amino acids in the primary polypeptide sequence
• Molecular chaperones are only present under what conditions?

  stress conditions/ heat shock
• What do molecular chaperones assist in?

  correct protein folding/refolding of polypeptide sequences
• What is protein processing?

  after initial translation, a process called post translational modification occurs

  these modifications include phosphorylation or glycoslation, modifying final protein structure
• What is protein transport?

  active transport that allow proteins to be directed to the proper location (cytoplasm, plasma membrane, etc)
• What is the main function of singal peptides?


  act as a zip code to direct protein to correct location; identify the final destination
• What happens in protein transport when the protein is properly located?

  the signal peptides are cleaved off
• Where do transcription and replication occur?

  nucleus
• Where does translation occur?


  cytoplasm
• What is the benefit of mutations?

  provide raw material for evolution
• What does a silent mutation result in?

  no change in the amino acid sequence of the protein
• What does a missense mutation result in?

  coding for a different amino acid at that position in the eventual protein
• What does a nonsense mutation result in?

  change that forms a stop codon where one shouldnt be found
• What would you expect if a mutation occurs in regulatory region (promoter)?

  there will be no RNA binding, no function will be active
• What does the promoter region do?

  binds RNA polymerase
• What do frameshift mutations alter?

  amino acid sequences of proteins
• What happens if you delete or insert in the start codon?

  impacts the product you want in polypeptide sequence/coding
• What is inversion of mutations?

  DNA becomes inverted at same location
• What is translocation of mutations?

  DNA segment "breaks off" and reattaches at different chromosome

  same chromosome but different location
• What is the impact of inversion?


  impacts outcome of amino acid sequence and protein
• What is the impact of translocation?

  impacts transcription and translation
• How can chemicals induce mutation?

  binds to completely different base; removing amino groups
• How can UV light affect induced mutations?

  forming thymine dimers
• What does ionizing radiation cause?

  double strand breaks in phosphate sugar backbone
• How can mutagens affect DNA?

  substitution of base pairs

  deletion or insertion of base pairs

  chemical modifications

  DNA strand breaks

  interference with DNA repair mechanisms