Download Microbes in Medicine and Research

Microbes in Medicine and
Research
Microbes and Society
Fall 2007
How are Microbes Used in
Medicine and Research
• Microbes are used to deliver “new” genes
in gene therapy.
• Microbes are used to clone genes so we
can study and identify them
• Microbes are used to commercially make
proteins such as insulin or human growth
hormone
Central Dogma Theory is Key to Using
Microbes for Medicine/Research
Eukaryotic and Prokaryotic Organisms
Some Viral Organisms
DNA Bases
DNA Nucleotides
• Adenine always pairs with Thymine (A-T)
• Cytosine always pairs with Guanine (C-G)
• Each nitrogenous base (A, T, C, G) is also
associated with a sugar (deoxyribose for
DNA) (ribose for RNA) and phosphate.
• Therefore, the name of DNA means
deoxyribonucleic acid and RNA stands for
ribonucleic acid.
Structure of a Nucleotide
DNA is assembled as a Double
Helix
DNA Replication is Adding
Nucleotides to the DNA Templates
End of Replication
• The entire double helix is copied.
Therefore, each chromosome is copied
and then 1 copy of each chromosome is
packaged in each cell. This occurs during
the cell cycle known as mitosis.
DNA to RNA (Transcription)
• In the nucleus, one region of DNA (one
that contains a gene) is transcribed into
RNA. This RNA is formally called
messenger RNA (mRNA).
• RNA differs from DNA in that it is single
stranded, and does not contain the
nucleotide Thymine (T), but instead
contains Uracil (U).
DNA to RNA
DNA
RNA
A-U
T-A
G-C
C-G
T-A
A-U
Therefore, DNA template is ATGCTA and the resulting RNA is UACGAU
mRNA can then Leave the Nucleus
• mRNA leaves the nucleus to associate
with a ribosome
• While in the ribosome, transfer RNA
(tRNA) carries amino acids to start
building proteins
• Each 3 nucleotides are known as a codon,
and each codon is specific for 1 of the 20
available amino acids.
Genetic Code for Amino Acids
Proteins are Modified
• After proteins are made at the ribosomes,
they are then modified by folding, cutting
and adding of sugars, etc.
• These proteins are what makes us what
we are and are also the proteins that
regulate our bodies on a daily basis.
What is a Gene?
• A gene is region of DNA that is heritable,
and can be transcribed and translated into
a usable product.
• Much of our DNA is not usable. We have
approximately 33,000 genes in our
genome.
What if a Gene is Faulty
• Medical advances has proposed gene
therapy as a possible solution to “fixing”
faulty genes.
• Microbes are often used as a delivery
method for the new gene.
• Virus can deliver DNA into cells that need
a new gene.
How do we add DNA to a Microbe
• We use restriction endonucleases to “cut”
DNA in a pattern that will allow a new
piece of DNA to be inserted.
• Restriction endonucleases are also known
as restriction enzymes and are also used
in DNA fingerprinting.
How do restriction enzymes work?
These enzymes search the length of DNA and make cuts when it finds
a specific pattern. In this example, EcoRI looks for the GAATTC pattern and
Whenever it sees it, cuts between the G and the A.
5'...GAATTC...3'
3'...CTTAAG...5'
Putting DNA together
• Cut the DNA of that contains the gene of
interest with a restriction enzyme
• Cut the DNA of a vector (virus, or bacteria)
with the SAME restriction enzyme
• Ligate (seal) the DNA from host and vector
together.
• Let the vector “infect” a new cell with the
new DNA.
We use Bacteria to Make Drugs