Chapter 14: Gene Mutation and Molecular Medicine

• What is the main topic of Chapter 14?

  From DNA to Protein: Gene Expression
• What is the first key concept in Chapter 14?

  Genes Code for Proteins
• What does the mutation in the mecA gene of MRSA result in?

  A protein that no longer binds methicillin and other antibiotics
• What disease is associated with a recessive mutant allele that produces homogentisic acid?

  Alkaptonuria
• What is the role of the enzyme affected by the mutation in alkaptonuria?

  It normally converts homogentisic acid to a harmless product
• What conclusion did Garrod reach regarding genes and enzymes?

  There must be one gene to one enzyme
• What was confirmed about the enzyme related to alkaptonuria in 1958?

  Homogentisic acid oxidase was identified as active in healthy people
• What is the revised hypothesis regarding genes and proteins?

  One-gene, one-polypeptide relationship
• What are model organisms used for in genetic studies?

  They are easy to grow, manipulate genetically, and produce large numbers of progeny
• What are the steps of gene expression?

  1. Transcription: DNA sequence is copied to RNA
  2. Translation: RNA sequence is used to synthesize a polypeptide
• What is the role of messenger RNA (mRNA) in gene expression?

  It is copied from DNA and moves to the cytoplasm for translation
• What is the function of ribosomal RNA (rRNA)?

  It catalyzes peptide bond formation between amino acids
• What does transfer RNA (tRNA) do?

  It binds specific amino acids and recognizes sequences in mRNA
• How do some viruses replicate their genetic material?

  By transcribing RNA to a complementary RNA strand
• What is reverse transcription in retroviruses?

  Making a DNA copy of their RNA genome
• What is the template for transcription?

  The base sequence of one strand of DNA
• What is required for transcription to occur?

  A DNA template, ribonucleoside triphosphates, and RNA polymerase
• In which direction do RNA polymerases add nucleotides during transcription?

  In a 5′-to-3′ direction
• What are the three steps of transcription?

  Initiation, elongation, and termination
• What is the role of sigma factors and transcription factors?

  They help direct RNA polymerase onto the promoter
• What happens during the elongation phase of transcription?

  RNA polymerase unwinds DNA and reads the template strand
• What is the termination of transcription specified by?

  A specific DNA sequence
• What happens to noncoding regions (introns) during RNA processing?

  They are sliced out of pre-mRNA in the nucleus
• What is added to the 5′ end of pre-mRNA during processing?

  A 5′ cap
• What does the poly A tail do for mRNA?

  It assists in export from the nucleus and stabilizes the mRNA
• What is the genetic code?

  A specification of which amino acids will be used to build a protein
• What is a codon?

  A sequence of three bases that specifies a particular amino acid
• What was the hypothesis tested by Nirenberg and Matthaei regarding artificial mRNAs?

  An artificial mRNA containing only one repeating base will direct synthesis of a protein with one repeating amino acid
• What is the significance of the start codon AUG?

  It is the initiation signal for translation and codes for methionine
• How many codons are there compared to amino acids?

  There are more codons than amino acids
• What does it mean that the genetic code is redundant?

  Most amino acids are specified by more than one codon
• What does it mean that the genetic code is not ambiguous?

  Each codon specifies only one amino acid
• What is the nearly universal aspect of the genetic code?

  The codons are the same in all organisms
• What is the role of transfer RNA (tRNA) in translation?

  It links mRNA codons with specific amino acids
• What is the function of ribosomes in protein synthesis?

  They translate the mRNA into a polypeptide
• How does knowledge of the genetic code help us understand the actions of some antibiotics?

  It allows us to identify mutations that confer resistance to antibiotics like methicillin
• What is the specific mutation in the mecA gene of MRSA?

  It results in a protein that no longer binds methicillin
• What is the significance of identifying homogentisic acid oxidase in healthy individuals?

  It confirms the role of the enzyme in the breakdown of homogentisic acid
• What is the role of the splicing machinery in RNA processing?

  It identifies and removes introns from pre-mRNA
• What does artificial mRNA containing only one repeating base direct the synthesis of?

  A protein containing only one repeating amino acid