MUTATION - SCI

• Mutation


  • Change(s) in the nucleotide/base sequence of DNA
  • due to errors in DNA replication
  • due to the impacts of chemicals
  • radiation to the DNA molecule
• Mutation may be based from

  • Chromosome number
  • Chromosome structure
  • Nucleotide sequence
• Euploidy

  • one or more than one complete set of chromosomes
• Aneuploidy


  • one or a few chromosomes above or below the normal chromosome number
• Non-disjunction

  1. Failure of chromosomes to separate during meiosis

  2. Causes gamete to have too many or too few chromosomes

  
• Chromosomal structure mutations


  • More extensive, altering the entire chromosomal structure
  • Changes the structure of whole chromosomes
• chromosomal structure mutations occur through

  • Deletions
  • Duplications
  • Inversions
  • Translocations
• Deletions


  If too much information is lost, it may be fatal to the organism and may result in early death https://o.quizlet.com/6jn9xamBy7xeDDjtM2sWSA.png
• Cri-du-chat syndrome(example of deletion)


  • a rare genetic disorder caused by a missing section on a particular chromosome known as Chromosome 5.
  • There is no cure

  
• Duplications


  • Effect depends on location within the chromosome
  • Whether or not duplication resides in coding or non-coding region of DNA
• Pallister-Killian mosaic syndrome


  • Caused by the presence of at least four copies of the short arm of chromosome 12 instead of the normal two
  • symptoms: coarse face with a high forehead, sparse hair on the scalp, an abnormally wide space between the eyes, a fold of the skin over the inner corner of the eyes, and a broad nasal bridge with a highly arched palate. Intellectual disability, loss of muscle tone, and streaks of skin lacking color are often present.
• Inversions


  Can be caused due to abnormal synapsis event at Meiosis I by incorrect chromosomes coming together
• Translocations


  • due to abnormal synapsis event at Meiosis by incorrect chromosomes coming together.
  • Associated with 2 forms of leukemia
• Hemophilia


  • Rare disorder in which the blood doesn't clot in the typical way because it doesn't have enough blood-clotting proteins (clotting factors)
• Point mutations


  • Affects single sites on DNA
  • Transition substitution - purine (A/G) or pyrimidine (T/C) substitutes for itself
  • Transversion substitution - purine substitutes for pyrimidine or vice versa
• Results of point mutations

  • Silent mutation
  • Missense mutation
  • Nonsense mutation
• Silent mutation


  • No change in amino acid sequence is produced due to redundancy of Genetic Code
• Missense mutation


  • Produces a change in amino acid sequence in protein product; may change function of protein or may not
• Sickle cell disease


  • A single base substitution in a hemoglobin gene causes blood cells to form abnormally
• Nonsense mutation


  Produces a STOP codon within the mRNA transcript leading to a truncated protein
• Frameshift mutations


  • Insertion or deletion of one or more nucleotides
  • Changes the "reading frame" like changing a sentence
  • Proteins built incorrectly

  
  

  • Original: The fat cat ate the old rat.
  • Frame Shift: The fat caa tet heo ldr at.
• Mutation is important for evolution
• If no changes to genomes occur over time, there would be no evolution
• Too much change in the DNA is harmful, too little does nothing
• A balance exists between the amount of new variation and the overall health (adaptiveness) of the new variant individual
• Mutations can change DNA

  • A mutation in one gene causes a fly to develop legs where its antenna should be
• A mutation is a change in a cell's DNA sequence
• Mutations come in several varieties
• The more contact a person has with mutagens, the higher the risk for cancer
• What can cause a mutation?

  • Inherited
  • Environmental agents
  • Spontaneous
• Mutagen


  Anything environmental that can cause a change in DNA
• Examples of mutagens


  • Radiation - UV, X-rays, nuclear
  • Chemicals - asbestos, formaldehyde, chemicals in tobacco products
• Many mutagens are also carcinogens - cancer causing
• Mutations are not always harmful
• Alleles


  Alternative versions of the same gene
• Genetic variation is important for evolution
• Plant breeders even induce mutations to create new varieties of plants
• Mutations can be bad, leading to cancer, aging, birth defects, self-aborted embryos
• Mutations on chromosome number

  • Euploidy
  • Aneuploidy
• Mutation on NUCLEOTIDE SEQUENCE

  • Point Mutation
  • Frameshift Mutations