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 DNARNA 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.Virus

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? 5'...GAATTC...3' 3'...CTTAAG...5' 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.

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