SCIENCE || Mutations

• Mutation


  Changes in the Genetic Code
• Mutation causes changes in the kind, sequence, and number of amino acids of proteins synthesized by cells

  Any change in the sequence of nitrogenous bases in the DNA, any mistake in the transcription of genetic information from DNA to RNA, or pairing of the codon and anticodon, may cause changes in proteins
• Factors that can induce mutation

  • Mutagens
  • Toxic chemicals
  • Harmful radiation
• Mutations can occur in two different types of cells: reproductive cells and body cells
• Only mutations in sex cells pass on to offspring
• If mutation is severe, the resulting protein may be nonfunctional, and the embryo may not develop
• Types of mutations in gamete cells

  • Gene mutation
  • Chromosomal mutation
• Most mutations are harmful
• Some mutations in a body cell can cause cancer, while mutations in sex cells can cause birth defects
• A severe mutation may lead to cell death and may have no effect on the body
• Sometimes mutations may be useful for the species
• Diseases caused by inherited genes are the result of mutations
• Gene Mutations involve changes in one or a few nucleotides and are known as point mutations
• Point mutations include substitutions, insertions, and deletions
• Substitutions involve changing one base to a different base
• Insertions and deletions are point mutations where one base is inserted or removed from the DNA sequence
• Insertions and deletions are also called frameshift mutations
• Chromosomal Mutations involve changes in the number or structure of chromosomes
• Types of chromosomal mutations

  • Deletion
  • Duplication
  • Inversion
  • Translocation
• Types of chromosomal mutations

  • Deletion
  • Duplication
  • Inversion
  • Translocation
• Deletion


  Involves the loss of all or part of a chromosome
• Duplication

  Produces an extra copy of all or part of a chromosome
• Inversion


  Reverses the direction of parts of a chromosome
• Translocation


  Occurs when part of one chromosome breaks off and attaches to another
• “Cri du chat” is caused by the deletion of part of the short arm of chromosome 5. Affected babies make high-pitched cries that sound like a cat. They have wide-set eyes, a small head and jaw, are moderately to severely mentally retarded, and very short.
• Down’s syndrome is usually caused by an extra copy of chromosome 21 (trisomy 21). Characteristics include decreased muscle tone, stockier build, asymmetrical skull, slanting eyes, and mild to moderate mental retardation
• Edwards syndrome is a trisomy of chromosome 18. Symptoms include mental and motor retardation, numerous congenital anomalies, and a characteristic hand appearance with clenched hands and overlapping fingers. About 99% die in infancy
• Jacobsen syndrome, also called terminal 11q deletion disorder, is a very rare disorder. Those affected have normal intelligence or mild mental retardation, with poor or excessive language skills. Most have a bleeding disorder called Paris-Trousseau syndrome
• Klinefelter’s syndrome (XXY) results in men who are usually sterile, have longer arms and legs, are taller than their peers, and have a higher incidence of speech delay
• Turner’s syndrome (X instead of XX or XY) results in females with underdeveloped female sexual characteristics, short stature, low hairline, abnormal eye features and bone development, and a “caved-in” appearance to the chest
• Chromosomal material can be lost or rearranged during the formation of gametes or cell division, leading to severe changes that may result in miscarriage or chromosomal abnormalities. One in 156 live births has some kind of chromosomal abnormality
• A karyotype is an image of the full set of chromosomes of an individual that displays the normal number, size, and shape. It can reveal the gender of a fetus or test for certain defects through procedures like amniocentesis
• Genetic engineering produces transgenic or GM crops and organisms by moving genes from one species into another. Recombinant DNA is formed when DNA from two different species are joined together
• Transgenic organisms can manufacture genetic products foreign to them using recombinant DNA. Genetic engineering has applications in bacteria, plants, and animals for human use, including medical applications like gene therapy and vaccines
• Organisms genetically engineered


  • Bacteria
  • Plants
  • Animals
• Organisms are engineered to be of use to humans
• Applications of recombinant DNA technology

  • Medical applications including gene therapy and vaccines
  • DNA fingerprinting used for identification in crimes and providing evidence for identity of deceased persons
  • Creation of genetically modified crops resistant to pesticides or producing extra vitamins and minerals
  • Bacteria used to clean oil spills
• Limitations of recombinant DNA technology are its potential effects on the ecosystem
• Steps in Genetic Engineering

  1. Effects of Mutations

  2. Mutagens

  3. Harmful and Helpful Mutations
• Genetic material can be altered by natural events or artificial means