Molecular Basis for

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Molecular Basis for Relationship between Genotype
and Phenotype
DNA
genotype
DNA sequence
transcription
RNA
translation
amino acid sequence
protein
function
organism
phenotype
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Molecular Genetic Diagnostics Sickle Cell Anemia
Electron Micrograph HbA codes for normal
b-globin and produces normal hemoglobin. HbS
produces sickled red blood cells. Homozygotes
for HbS are anemic. HbS produces b-globin that
differs from normal protein by one amino acid.
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Molecular Genetic Diagnostics Sickle Cell Anemia
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Molecular Genetic Diagnostics Sickle Cell Anemia
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Methods of introducting a transgene
Solution of DNA to be studied is injected into
host cell.
Recombinant DNA can be delivered into host cell
using a viral vector.
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Methods of introducting a transgene
Bombardment with DNA-coated tungsten particles
introduces DNA into host cell.
Under favorable conditions, DNA can be taken up
by host cell by transformation.
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Molecular Basis for Relationship between Genotype
and Phenotype
DNA
genotype
DNA sequence
transcription
RNA
translation
amino acid sequence
protein
function
organism
phenotype
8
Transgenesis

• Introduction of foreign genetic material into a
  host organism.
• 2. Ability of the new genetic material to be
• transmitted to offspring of the host.
• 3. Potential of the new genetic material to
• be expressed in the host.
• 4. Transgenic animals or transgenic plants
• are the result of this process.

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Agrobacterium tumefaciens (soil bacterium) causes
crown gall disease in infected plants.
Ti (tumor-inducing) plasmid is 200-kb
double-stranded circular DNA.
T-DNA region is transferred and randomly inserted
into host plant genome. T-DNA directs tumor
production and synthesis of opines, compounds
that the bacterium needs for growth.
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Genetic Engineering in Plants using Ti Plasmid
T-DNA can be replaced by DNA sequence of interest
and introduced into host plant genome. Reporter
genes (selectable markers) are spliced into the
recombinant T-DNA. Successful integration is
indicated by expression of reporter genes.
Markers (reporter genes) such as kanamycin
resistance gene are very useful in monitoring
successful transformation.
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Generation of a Transgenic Plant
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Genetic Engineering in Plants
Plants that have been transformed include
horse-radish, morning glory, cucumber, carrot,
yam, cotton, sunflower, lettuce, tomato, corn,
soybean, alfalfa, tobacco, potato, and
clover. Agriculturally important crops can be
engineered to express - viral resistance -
pesticide resistance - herbicide resistance -
insect resistance Nutritional value can be
enhanced, for example, by introduction of genes
that increase seed protein content. Plants can
be engineered to produce pharmaceutically
important proteins or vaccines.
Luciferase gene is useful as a reporter gene for
transformation.