Sources of DNA 4.2

Introduction In nature, DNA is made in cells. For sources of DNA, scientists can find cells in nature or they can grow cultures of cells in the lab. Scientists have learned to grow many different cells on or in a medium (source of nutrients) prepared in the lab. Cells from cell cultures can be collected & broken open in a process called lysis. Lysed cells release their DNA in a mixture of other cellular molecules. Through separation techniques, DNA can be isolated from the other cell molecules.

Prokaryotic DNA Found in cytoplasm in small rings called PLASMIDS and/or in a long supercoiled shape. Plasmids only contain a few genes (5-10). Example: Gene for antibacterial resistance. Grows will in a liquid broth or solid medium called agar.

Types of Mediums Solid Agar Liquid luria broth solution.

Eukaryotic DNA (Mammalian Cell Culture) More challenging to grow than bacterial cells. Why? Cells grow within multicellular organisms & depend on other cells for many products & stimuli. Grown in broth culture tubes & bottles. Large-scale—produced in fermentation tanks.

Mammalian Cell Cultures Any idea why the medium is red?

Viral DNA Nonpathogenic viruses are used in biotech research as vectors to carry DNA between cells. They can insert corrective genes (gene therapy) into cells that contain defective genes. Ex. Cystic fibrosis Viral DNA is short & easy to manipulate. They may be cut open to insert genes of interest.