chapter 14

• What are chromosomes made up of?

  Genes
• What are genes made up of?

  Sequences of DNA nucleotides

  
• What does DNA carry?

  Instructions for making proteins
• What are proteins responsible for?

  Phenotypic traits like eye color
• What is the flow of genetic information?

  • DNA → mRNA → Protein
  • DNA dictates protein synthesis
  • Proteins determine organism's traits

  
• What is the relationship between genotype and phenotype?

  Proteins link genotype to phenotype
• What can a single faulty gene result in?

  A different appearance
• How do genes specify proteins?

  • Through transcription and translation
  • Transcription synthesizes mRNA
  • Translation synthesizes proteins

  
• Who first suggested that genes dictate phenotypes?

  Archibald Garrod
• What did Garrod believe caused symptoms of inherited diseases?

  Inability to synthesize a certain enzyme
• What is a metabolic pathway?

  • Series of steps for synthesizing and degrading molecules
  • Involves enzymes catalyzing reactions
  • Links genes to enzyme function
• What is the central dogma of molecular biology?

  DNA → mRNA → Protein

  
• What is transcription?

  Synthesis of mRNA under DNA direction

  
• What is translation?

  Synthesis of protein from mRNA

  
• Where does translation occur?

  Ribosomes
• How is mRNA processed in prokaryotes?

  Immediately translated without processing

  
• How is mRNA processed in eukaryotic cells?

  Modified through RNA processing

  
• What is the template strand in transcription?


  One DNA strand providing a template

  
• In which direction are codons read during translation?

  5′ to 3′ direction
• What do codons specify?

  Amino acids in a polypeptide
• What is the genetic code?

  • 64 codons total
  • 61 code for amino acids
  • 3 are stop signals
  • Redundant but not ambiguous

  
• Why must codons be read in the correct reading frame?

  To produce the specified polypeptide
• How universal is the genetic code?

  Nearly universal across species
• What are the stages of transcription?

  1. Initiation
  2. Elongation
  3. Termination

  
• What catalyzes RNA synthesis?

  RNA polymerase
• What is the promoter in transcription?

  DNA sequence where RNA polymerase attaches

  
• What is the terminator in bacteria?

  Sequence signaling the end of transcription

  
• What is a transcription unit?

  Stretch of DNA that is transcribed

  
• What happens during the initiation of transcription?

  • RNA polymerase binds to the promoter
  • Transcription factors mediate binding
  • Transcription initiation complex forms

  
• What is the TATA box?

  A promoter crucial for initiation in eukaryotes

  
• How does RNA polymerase elongate the RNA strand?

  Untwists DNA and adds nucleotides
• What is the rate of transcription in eukaryotes?

  40 nucleotides per second
• What happens at the end of transcription?

  RNA polymerase II stops at the terminator

  
• What modifications occur during RNA processing in eukaryotes?

  • 5′ cap added
  • Poly-A tail added
  • Introns removed, exons spliced
• What is the function of the 5′ cap and poly-A tail?

  Facilitate export and protect mRNA
• What are introns?

  Noncoding regions in RNA transcripts
• What are exons?

  Regions that are expressed in proteins
• What is RNA splicing?

  • Removal of introns
  • Joining of exons
  • Creates continuous coding sequence
• What carries out RNA splicing?

  Spliceosomes
• What are ribozymes?

  Catalytic RNA molecules that splice RNA