Chapter 17

• What is gene expression?

  Process by which DNA directs protein synthesis
• What did Beadle and Tatum discover?

  Genes dictate the production of specific enzymes
• What is the one gene-one enzyme hypothesis?

  A gene dictates the production of a specific enzyme
• How has the one gene-one enzyme hypothesis been modified?

  Eukaryotic genes can code for multiple polypeptides
• What are three ways RNA differs from DNA?

  RNA is single-stranded, has ribose, and uracil
• What is transcription?

  Synthesis of RNA using DNA information

  
• What is translation?

  Synthesis of polypeptides using mRNA information

  
• What is the summary of transcription and translation processes?

  • Transcription: DNA → RNA in the nucleus
  • Translation: mRNA → Polypeptides at ribosomes

  
• What is the template and product of transcription?

  Template: DNA; Product: RNA

  
• Where does transcription occur in eukaryotic cells?

  Nucleus
• What is the template and product of translation?

  Template: mRNA; Product: Polypeptides
• Where does translation occur in eukaryotic cells?

  Ribosomes
• What is the Central Dogma of molecular biology?

  DNA → RNA → Protein
• How many codons are in the RNA strand 3’ A C G A C C A G T A A A 5’?

  3 codons
• What is the difference between the template strand and the coding strand in DNA?

  Template strand is used for RNA synthesis
• How did Marshall Nirenberg crack the genetic code?

  Synthesized artificial mRNA with uracil
• How many possible codons are there?

  64 codons
• How many codons actually code for amino acids?

  61 codons
• What is the start codon?

  AUG
• What do the codons UAA, UAG, or UGA represent?

  Termination or stop codons
• What is the reading frame in translation?

  Groups of 3 nucleotides must be read correctly
• What happens if the reading frame is altered?

  Amino acid sequence is changed
• What enzyme is involved in transcription?

  RNA polymerase
• What is a transcription unit?

  Region of DNA transcribed into RNA
• What are the three stages of transcription?

  1. Initiation: RNA polymerase binds to promoter
  2. Elongation: RNA transcript is synthesized
  3. Termination: RNA transcript is released

  
• What is the transcription initiation complex?

  Assembly of transcription factors and RNA polymerase
• What modifications occur to the primary transcript in eukaryotic cells?

  5’ cap and poly-A tail added
• What are the functions of the 5’ cap and poly-A tail?

  Facilitate export, protect mRNA, help ribosomes
• What is the difference between introns and exons?

  Introns are noncoding; exons are coding
• What is a spliceosome?

  Complex of proteins and RNA that splices RNA
• What is alternative RNA splicing?

  Produces different mRNA from the same transcript
• What is a ribozyme?

  RNA molecule that functions as an enzyme
• What properties of RNA enable it to function as an enzyme?

  Single-stranded, functional groups, hydrogen bonding
• What are the types of RNA and their functions?

  • mRNA: Carries genetic info from DNA
  • tRNA: Translates nucleic acid to protein
  • rRNA: Forms ribosomes with proteins

  
• What is an anticodon?

  Nucleotide triplet on tRNA that pairs with mRNA
• What do aminoacyl-tRNA synthetases do?

  Join amino acids to the appropriate tRNA
• What are the stages of translation?

  1. Initiation: mRNA, tRNA, and ribosome assemble
  2. Elongation: Amino acids added to polypeptide chain
  3. Termination: Release factor binds to stop codon
• What is a release factor?

  Protein that binds to stop codon
• What are types of post-translational processing?

  Chemical modifications, amino acid removal, subunit assembly
• What determines ribosome location in the cell?

  Amino acid sequence of the protein being synthesized