1.3 Gene Expression

• What determines an organism's phenotype?

  Proteins produced from gene expression
• How many genes in a cell are typically expressed?

  Only a fraction of the genes
• What regulates gene expression?

  Transcription and translation processes
• What determines a cell's genotype?

  Sequence of DNA bases in its genes
• What happens to genes in a specialized cell?

  Only necessary genes are switched on
• What is the process of differentiation in cells?

  It involves changes in gene expression
• What is gene expression?

  Activation of a gene resulting in protein formation
• What influences gene expression?

  Intra- and extra-cellular environmental factors
• Why do different cells require different proteins?

  Different functions necessitate different gene expression
• What is the structure of RNA?

  RNA is single stranded
• What base does RNA contain instead of thymine?

  Uracil
• What sugar does RNA contain?

  Ribose
• What is the role of mRNA?

  It carries DNA code to the ribosome
• What forms the ribosome along with proteins?

  Ribosomal RNA (rRNA)
• What does each tRNA carry?

  A specific amino acid
• What is the primary structure of a protein?

  The polypeptide chain of amino acids
• What forms the secondary structure of a protein?

  Weak hydrogen bonds between amino acids
• What is the tertiary structure of a protein?

  The final structure due to bonding interactions
• What are fibrous proteins formed from?

  Several polypeptide chains in parallel strands
• What do globular proteins resemble?

  A tangled ball of string
• What is quaternary structure in proteins?

  Bonding of several polypeptides together
• What is a conjugated protein?

  Contains polypeptide chains and a non-protein part
• What are some functions of proteins?

  Enzymes, structural, hormones, antibodies
• What is gel electrophoresis used for?

  To separate proteins by size
• What is the process of transcription?

  • DNA is transcribed into primary RNA
  • RNA polymerase binds to DNA promoter
  • Introns are removed, exons joined in splicing
  • Mature mRNA exits the nucleus
• What is the process of translation?

  • mRNA is translated into a polypeptide
  • tRNA brings amino acids to ribosome
  • Codons on mRNA match anticodons on tRNA
  • Peptide bonds form between amino acids
• What is alternative RNA splicing?

  • Different segments treated as exons/introns
  • Same primary transcript can produce multiple mRNAs
  • Leads to diverse polypeptide chains from one gene
• What holds proteins in their 3D shape?

  • Peptide bonds
  • Hydrogen bonds
  • Interactions between amino acids
• What are the four levels of protein structure?

  1. Primary: Polypeptide chain
  2. Secondary: Coils and folds
  3. Tertiary: Final 3D shape
  4. Quaternary: Multiple polypeptides bonded
• What are the roles of enzymes in proteins?

  • Catalyze biochemical reactions
  • Lower activation energy
  • Increase reaction rates
• What are the roles of structural proteins?

  • Provide support and shape
  • Form cellular structures
  • Contribute to tissue integrity
• What are the roles of hormones in proteins?

  • Regulate physiological processes
  • Act as signaling molecules
  • Maintain homeostasis
• What are the roles of antibodies in proteins?

  • Identify and neutralize pathogens
  • Provide immune defense
  • Bind to specific antigens