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Insertion Mutations. What is an insertion mutation?. Mutations caused by the insertion of DNA bases or fragments This can happen when DNA is copied incorrectly ( frameshift mutation) One or two bases are added This can also happen when large fragments move from one place to another.

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what is an insertion mutation
What is an insertion mutation?
  • Mutations caused by the insertion of DNA bases or fragments
  • This can happen when DNA is copied incorrectly (frameshift mutation)
    • One or two bases are added
  • This can also happen when large fragments move from one place to another
barbara mcclintock
Barbara McClintock
  • Genes and chromosomes were originally described as “beads on a string”; it was thought that genes occupied a fixed position on a chromosome
  • Barbara McClintock received a Nobel prize in 1983 for her workdiscovering transposable elements or “jumping genes”: DNA fragments that can move from one chromosome to another.
  • Today we know that 65% of the human genome is composed of transposable elements
mcclintock s observations
McClintock’s Observations:
  • McClintock discovered transposons by studying colour pattern in Indian corn
  • She found that corn kernels which should have been brown or purple according to their genotype, would often show patches of white
  • She correctly predicted that this happened if a transposon inserted itself and disrupted the pigment producing gene.
    • Also seen in hosta plants
  • Viruses contain genetic information, but are not living things.
  • In order to make copies of themselves, they rely on cell machinery of the host
  • Viruses insert their DNA into the host’s genome, so the host will transcribe and translate viral genes in order to make viral proteins
  • Throughout evolution, our DNA has acquired many relics of past viral infection.
  • Once the human genome was sequenced in 2000, it was found that ~ 8% of our genome is from viruses!
  • Like transposons, when viral DNA is inserted in the middle of a human gene, its function will be disrupted.
  • Viral insertions usually occur in regulatory genes, which increase or decrease the function of another gene
negative effects of viral insertions
Negative effects of viral insertions
  • Insertions can be harmful
    • If viral genes disrupt genes that regulate cell growth, infection may cause cancer = oncovirus
      • HPV (Human Papilloma Virus)
      • Hepatitis C Virus
    • Prior infection with certain viruses has been linked to the development of other diseases.
      • Bornavirusschizophrenia and other mood disorders.
      • Herpes virus 1 Alzheimer’s
benefits of viral insertions
Benefits of viral insertions
  • Insertions can be beneficial
    • Viral insertions have activated some digestive enzymes in human saliva by disrupting suppressor genes
    • Infection by less harmful virus prevents infection by more dangerous strains.
      • Vaccinia prevents small pox
    • Viral machinery can be manipulated to insert helpful genes into cells (gene therapy)
genetics and probability homework
Genetics and Probability Homework
  • 0.50 that 1st child will be brown-eyed (depends on inheriting B from dad: Bb)

2. a) 0.25 (both are HRHW, 0.50 that each pass on HR allele)

b) 0.50 ( 0.25 probability of each combination, 2 combinations produce roan cattle)

  • a) cross 1: 0.50; cross 2: 0.00; cross 3: 0.25

b) cross 1: 0.50; cross 2: 0.50; cross 3: 0.50

c) cross 1: 0.00; cross 2: 0.50; cross 3: 0.25

  • a) affected son: 0.50 affected daughter: 0.00

b) affected son: 0.25 (50% mom is a carrier x 50% she will pass on alllele); affected daughter: 0.25

  • man: Rr bb woman: rr BB

a) left handed child: 0.50

b) left handed with brown eyes: 0.50 (probability of brown eyes is 1.00)

6. Condition is recessive; 0.50 that carrier female will pass on affected allele, 0.67 that man is a carrier, 0.50 that man will pass on affected allele

0.50 x 0.67 x 0.50 = ~ 0.18 that they will have an affected child.