Chapter 15: From DNA to Protein - Gene Expression

• What is the main topic of Chapter 15 in the study material?

  Gene Mutation and Molecular Medicine
• What are the key concepts covered in Chapter 15?

  • Mutations are heritable changes in DNA
  • Mutations in humans can lead to diseases
  • Mutations can be detected and analyzed
  • Genetic screening is used to detect diseases
  • Genetic diseases can be treated
• What is the breast cancer gene mentioned in the study material?

  BRCA1
• What did Angelina Jolie do after learning about her BRCA1 mutation?

  She had both breasts removed to reduce the chance of getting breast cancer.
• What is a mutation?

  A change in the nucleotide sequence that can be passed on from one cell or organism to another.
• What are somatic mutations?

  Mutations that occur in body cells and are passed to daughter cells in mitosis but not to offspring.
• What are germ line mutations?

  Mutations that occur in cells that give rise to gametes and are passed to offspring at fertilization.
• What are loss of function mutations?

  Mutations where the gene is not expressed at all, or the protein does not function; nearly always recessive.
• What are gain of function mutations?

  Mutations that produce a protein with altered function; usually dominant and common in cancer.
• What is a conditional mutation?

  A mutation where the phenotype is altered only under certain restrictive conditions.
• What is a reversion mutation?

  A mutation where the gene is mutated a second time, reverting to the original sequence or a non-mutant phenotype.
• What are point mutations?

  Mutations involving insertion, deletion, or substitution of a single base pair.
• What are the two types of base pair substitutions?

  Transition and transversion.
• What is a silent mutation?

  A substitution that results in a codon that codes for the same amino acid.
• What is a missense mutation?

  A substitution resulting in a codon for a different amino acid.
• How does sickle-cell disease relate to mutations?

  It involves one amino acid substitution in the β-globin polypeptide, resulting in sickle-shaped cells.
• What is a nonsense mutation?

  A base substitution that results in a stop codon, leading to a shortened protein.
• What is a loss of stop mutation?

  A base pair substitution that changes a stop codon to a sense codon, adding extra amino acids to the polypeptide.
• What is a frame-shift mutation?

  An insertion or deletion of a base pair that alters the mRNA reading frame during translation.
• How can mutations outside coding regions affect genes?

  Promoter mutations may alter the rate of transcription, and mutations at RNA splicing sites may lead to abnormal mRNA.
• What are chromosomal rearrangements?

  Extensive changes in DNA caused by DNA molecules breaking and rejoining, disrupting genetic sequences.
• What is deletion in the context of chromosomal mutations?

  A chromosome breaks in two places and rejoins, leaving out part of the DNA.
• What is duplication in chromosomal mutations?

  Homologous chromosomes break at different positions and reconnect to the wrong partners.
• What is inversion in chromosomal mutations?

  A chromosome breaks and rejoins with one segment flipped.
• What is translocation in chromosomal mutations?

  A segment of DNA breaks off and attaches to another chromosome, potentially causing duplications and deletions.
• How can retroviruses affect mutations?

  They insert their DNA into the host genome at random, potentially causing loss of function mutations.
• What are transposons?

  Transposable elements that insert themselves into genes and cause mutations.
• How do transposons contribute to gene duplication?

  Some transposons replicate, and copies are inserted into new sites, sometimes carrying along genomic DNA.
• What are spontaneous mutations?

  Mutations that occur with no outside influence, often due to mistakes during replication.
• What can cause spontaneous mutations?

  Mistakes during replication and the existence of tautomeric forms of bases.
• How can chemical reactions lead to mutations?

  Chemical reactions can alter bases, such as deamination of cytosine converting it to uracil.
• What is an induced mutation?

  A mutation caused by an agent from outside the cell, known as a mutagen.
• What are some examples of chemical mutagens?

  Nitrous acid, which can deaminate cytosine and convert it to uracil.
• How does radiation damage DNA?

  Ionizing radiation creates highly reactive free radicals that can change bases into unrecognizable forms.
• What is the effect of UV radiation on DNA?

  UV radiation can cause thymine to form covalent bonds with adjacent bases, disrupting DNA replication.
• What are some natural sources of mutagens?

  Plants produce many chemicals for defense that can be mutagenic and carcinogenic, such as aflatoxin.
• What are nitrites and their role as mutagens?

  Nitrites are human-made mutagens used to preserve meats and can deaminate cytosine.
• What is a "hot spot" for mutations?

  Regions in DNA, such as 5-methylcytosine, that are more vulnerable to mutation.
• How can mutations provide benefits to organisms?

  They provide genetic diversity for natural selection and may cause advantageous changes in offspring's phenotype.
• How does gene duplication contribute to evolution?

  Gene duplication through transposon movements or chromosome rearrangement can provide genetic variation.