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Molecular Basis for
Relationship between Genotype and Phenotype
genotype
DNA
DNA sequence
transcription
RNA
translation
protein
function
phenotype
organism
amino acid
sequence
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.
Molecular Genetic Diagnostics: Sickle Cell Anemia
Molecular Genetic Diagnostics: Sickle Cell Anemia
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.
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.
Molecular Basis for
Relationship between Genotype and Phenotype
genotype
DNA
DNA sequence
transcription
RNA
translation
protein
function
phenotype
organism
amino acid
sequence
Transgenesis
1. 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.
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.
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.
Generation of a Transgenic Plant
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.
Luciferase gene is useful as a
reporter gene for transformation.
Plants can be engineered to produce
pharmaceutically important proteins or
vaccines.