CYTO

• Genetic mutation


  Change in the information contained in genetic material
• Genetic mutation


  • Change in the nucleotide/base sequence of DNA
  • Molecular change to the amino acids that make up DNA, responsible for coding for our genes
  • May occur due to errors in DNA replication or due to the impacts of chemicals or radiation to the DNA molecule
• An organism's DNA affects how it looks, how it behaves, its physiology — all aspects of its life. So a change in an organism's DNA can cause changes in all aspects of its life.
• Mutations can be beneficial, neutral, or harmful for the organism, but mutations do not "try" to supply what the organism "needs." Whether a particular mutation happens or not, it is unrelated to how useful that mutation would be.
• Mutations are responsible for the diversity we see between organisms, but they are also at the root of some diseases. They have vastly different consequences depending on the segment of DNA they affect and how they alter it.
• In the U.S., where people use shampoos with particular chemicals in order to kill lice, humans have a lot of lice that are resistant to the chemicals in those shampoos

  There are two possible explanations: 1) Resistant strains of lice were always there and are just more frequent now because all the non-resistant lice died, 2) Exposure to lice shampoo actually caused mutations for resistance to the shampoo
• This video segment tells the story of a genetic mutation affecting the human population of West Africa. Although helpful in preventing malaria, this mutation can also lead to sickle cell anemia.
• Mutations can be grouped according to

  • Their sizes
  • Phenotypic effects
  • The cause of occurrence
  • The type of cell in which they occur
• Germline mutations


  Hereditary mutations, alterations to the normal human DNA sequence that are passed down from parent to child and exist in almost every cell in the human body
• Somatic mutations


  Acquired mutations, mutations that a person was not born with, and they can arise at any point in a person's life
• Illnesses related to a combination of environmental factors and mutations in multiple genes include arthritis, Alzheimer's disease, cancer, diabetes, heart disease, high blood pressure, and obesity.
• Somatic mutations


  Occur in body cells, may have little effect on the organism, cannot be passed on to offspring
• Germline mutations


  Occur in gametes, can be transmitted to offspring, every cell in the offspring will have the mutation
• If a parent carries a gene mutation in their egg or sperm, it can pass to their child. These hereditary (or inherited) mutations are in almost every cell of the person's body throughout their life. Other mutations can happen on their own during a person's life, such as from damage from the sun's ultraviolet radiation or exposure to some types of chemicals. These mutations are not passed from parents to their children.
• Causes of mutation


  • DNA fails to copy accurately
  • A change in one or more nucleotides of DNA
  • A change in many genes
  • Loss of one or more genes
  • Rearrangement of genes or whole chromosomes
• Most of the mutations that we think matter to evolution are "naturally-occurring."
• External influences that can cause mutation

  • Mutagens
• Types of mutation


  • Chromosomal mutations
  • Gene mutations
• Chromosomal mutation


  An abnormal change in the entire structure of a chromosome or in the number of chromosomes an organism has
• Trisomy 21


  • Normal humans have 46 chromosomes, humans with Down Syndrome have 47
• Aneuploidies of sex chromosomes

  • Structural chromosomal abnormalities
• Robertsonian translocation


  A type of chromosome rearrangement involving the exchange between the proximal short arms of the acrocentric chromosomes 13, 14, 15, 21 and 22. The most common is between chromosomes 13 and 14. Carriers are asymptomatic but often produce unbalanced gametes that can result in miscarriage.
• Reciprocal translocation


  A type of chromosome rearrangement involving the exchange of chromosome segments between two chromosomes that do not belong to the same pair of chromosomes. Carriers of balanced reciprocal translocation are healthy persons but can produce gametes with unbalanced chromosomal material.
• Inversion


  Occurs when the segment between two breakpoints is inverted before rejoining the breaks
• Unbalanced structural rearrangements


  • Deletion
  • Inversion
  • Duplication
  • Nondisjunction
• Deletion


  Due to breakage, a piece of a chromosome is lost
• Duplication


  Occurs when a gene sequence is repeated
• Ring chromosome


  Two ends of the segment between breakpoints are joined to form a circular structure
• Nondisjunction


  Failure of chromosomes to separate during meiosis, causes gamete to have too many or too few chromosomes
• Gene mutation


  A change that affects a DNA at the molecular level by changing the normal sequence of a nucleotide base pairs, causes the cell to produce abnormal proteins
• Types of gene mutation

  • Substitution or point mutation
  • Frameshift mutation (deletion mutation, insertion mutation)
• Substitution mutation - point mutation

  Occurs when a nucleotide is replaced with a different nucleotide in the DNA sequence, only affects the codon for a single amino acid
• Frameshift - deletion mutation


  Deletion is the removal of a nucleotide from the DNA sequence, removal of even a single nucleotide alters every codon after the mutation
• Frameshift - insertion mutation

  The addition of one or more nucleotide base pairs into a DNA sequence
• Some mutations cause disease, some mutations may improve an organism's survival (beneficial), and some mutations lead to speciation.
• Videos about genetic mutations

  • 2077 - 10 Seconds to the Future - Mutation
  • Genetic Mutations - Hidden Secret
  • Bandila: What to know about hereditary diseases, genetic disorders
  • 18 Genetically Modified Organisms You Don't Know About