Genes, Chromosomes,

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Genes, Chromosomes, Genetic Change
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Gene

• A segment of DNA that helps to control a
  particular hereditary trait
• EX eye color
• genes are found on chromosomes

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Chromosome

• Structures made up of DNA found in the nucleus
  of cells

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• Any change in the DNA sequence
• Can have positive effects, negative effects, but
  usually has no effect (neutral)
• Mutations that occur on sex cells may be passed
  on to offspring mutations that occur in body
  cells cannot be passed on
• Mutations happen regularly many are repaired by
  enzymes

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Mutagen

• A substance or condition that causes an increase
  in the rate of mutation
• Ex errors in replication, transcription, cell
  division or by external agents such as
  viruses, extreme high temperatures, industrial
  chemicals, pesticide, cigarette smoke, food
  additives, radiation, UV light, etc.

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Gene mutation

• Point mutation the wrong base is put into a
  codon of a gene (substitution)
• EX GAG to GUG wrong amino acid
  a different protein
• sickle cell anemia is caused by a point mutation

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Gene mutation

• Frameshift mutation an extra bases is added
  or taken out a shift in the genetic
  code many amino acids are changed
  instead of just one
• EX The dog ate the cat (add a letter o
  after first codon) The odo gat eth eca t - -

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Chromosome mutations

• May involve
• -changing the structure of a chromosome
• -the loss or gain of part of a chromosome

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Chromosome mutation

• Inversion a piece of the chromosome is broken
  becomes reinserted backwards

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Chromosome mutation

• Translocation a piece of the chromosome
  breaks off and attaches to another chromosome
  pair

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Chromosome mutation

• Deletion part of a chromosome breaks off is
  lost

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• Insertion (Duplication) - occurs when a gene
  sequence is repeated

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Chromosome mutation

• Nondisjunction chromosomes fail to separate
• Monosomy zygote missing a chromosome
  death
• Trisomy zygote contains an extra chromosome
  EX Trisomy 21 Downs Syndrome

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Chromosome mutation

• Polyploidy nucleus doesnt undergo a second
  division during meiosis and the result is extra
  chromosomes (3n) , (4n)

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