Chapter 9 and Section 84: Genetic Engineering

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Chapter 9 (and Section 8-4)Genetic Engineering

• Section 9-1
• Breeding New Organisms

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The Appaloosa Horse

• The result of 200 years of selective breeding
  choosing to mate individuals with desired
  characteristics
• Very strong, good temperament

3
Selective Breeding

• Concept behind pure bred cats and dogs, also used
  for crop plants
• Individual organisms with desired characteristics
  are chosen to produce the next generation.

4
Hybridization

• Selective breeding of dissimilar individuals
  (different characteristics)
• Way to combine the best characteristics of two
  organisms
• Ex. plant with disease resistance crossed with
  plant that produces a lot of food

5
Inbreeding

• Selective breeding of similar individuals
  (similar characteristics)
• Way to maintain breed once it is established
  ensures preservation of the traits that make that
  breed unique
• Problems arise because members of the same breed
  are so genetically similar, the chances of
  recessive alleles pairing in increased, leading
  to genetic defects

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Mutations

• A mutation is an inheritable change in genetic
  information
• Error in DNA replication
• Two types
• Chromosomal mutations
• Gene mutations

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Chromosomal Mutations

• Change in the number or structure of an cells
  chromosomes
• Chromosome number mutations occurs in meiosis
  when an entire set of chromosomes fails to
  separate (different from nondisjunction!!)
• Leads to polyploidy three or more sets of
  chromosomes (fatal in animals, healthy in plants)

8
Chromosomal Mutations

• Chromosome structure mutations include
• Deletion - whole gene is deleted (Prader-Willi)
• Duplication - one gene on a chromosome is
  duplicated
• Inversion - pieces of the same chromosome invert
  (switch)
• Translocation piece of one chromosome breaks
  off and is reattached to another chromosome

9
Gene Mutations

• Affect only a single gene
• May involve one or more nucleotides
• Can have dramatic consequences
• Two main types
• Point mutations
• Frameshift mutations

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Point Mutations

• Involve a single nucleotide
• A substitution occurs when one nucleotide is
  substituted for another nucleotide, causing a
  change in one of the amino acids in the sequence

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Frameshift Mutations

• Involve the insertion or deletion of a nucleotide
• Cause a shift in the reading frame, altering
  the whole sequence past the point of mutation
• The fat car ate the rat
• Deletion Tef atc ata ter her at
• Insertion Thh efa tca tat eth era t

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Mutations and Breeding

• Most mutations are harmful, some can be desirable
• Sometimes, breeders attempt to increase the rate
  of mutations by exposing organisms to mutagens
  (mutation-causing agents) like X-rays, UV light,
  certain chemicals