 Naturally occurs in cells  Scientists use cell cultures as a source of DNA  Different types of cells are grown in mediums  Cell cultures are collected and lysed to extract DNA

 Do not contain a nucleus or any other membrane bound organelles  DNA is usually found floating in cytoplasm  attached at one spot to the cell membrane  One, long, circular chromosome  supercoiled  relatively small, several thousand genes  Very little spacer DNA  Most DNA is necessary for survival

 Plasmids  5 to 10 genes  Code for proteins that offer some additional characteristic that may be needed only under extreme conditions

 R Plasmids  contain antibiotic resistance genes  allows bacteria to survive antibiotics  transferrable  allows bacteria to "evolve" into an antibiotic resistant disease  Scientists use this feature to transfer "genes of interest" and transform bacteria genes

 Different kinds of plasmids  Some bacteria have no plasmids  Some bacteria have more than one kind  Often used as recombinant DNA vectors (rDNA) to transform cells  Cell will read DNA and synthesize proteins  Prokaryotic genes can be turned of during gene expression using only a few controls  Makes the cells favorable for protein synthesis

 R- Plasmids- a type of plasmid that contains a gene for antibiotic resistance.  Transformed- refers to those cells that have taken up foreign DNA and have started expressing the genes on the newly acquired DNA  Vector- a piece of DNA that carried one or more games into a cell, usually circular as in plasmid vectors  Operon- a section of prokaryotic DNA consisting of one or more genes and their controlling elements

 RNA polymerase- an enzyme that catalyzes the synthesis of complementary RNA strands from a given DNA strand  Promoter- the region at the beginning of a gene where RNA polymerase binds; the promoter “promotes” the recruitment of RNA polymerase and other factors required for transcription.  Operator- a region on an operon that can either turn on or off expression of a set of genes depending on the binding of a regulatory molecule.

 Beta-galactosidae- an enzyme that catalyzes the conversion of lactose into monosaccharides.  Figure 4.7 shows the prokaryotic cell of E.coli.  Figure 4.8 shows the structure of a bacterium showing the flagella, cytoplasm, cell wall, chromosome and plasmid.  Figure 4.9 shows beige and blue-black colonies of bacteria transformed.  Figure 4.10 shows an operon containing the controlling elements that turn genetic expressions On and Off.

 Bacterial Cell Culture  Two types of mediums  agar  solid  broth  liquid  reproduce quickly because cells have better access to nutrients

 Several chromosomes per cell  each chromosome is a single, linear, very long molecule of DNA  may contain several million or more nucleotides  may contain several thousands of genes  Eukaryotic Genome is substantially larger than that of prokaryotes  Bacterial cells have one chromosome  Humans have 46 chromosomes

 The total amount of DNA per cell is not directly related to an organism’s complexity.  Much of eukaryotic DNA is noncoding meaning that is does not transribe into protein  Eukaryotes have a lack of operators in their DNA, meaning that gene expression is controlled differently  They are usually expressed at a very low level  Increases occur when enhancer molecules interact with the RNA polymerase or with other enhancer DNA regions where molecules attach to the DNA and increase gene transcription

 At the structural DNA, RNA polymerase enzyme builds a complementary mRNA transcript from one side of the DNA strand; the enzyme transcribes the entire gene until it reaches a terminal sequence  In eukaryotes, mRNA is often modified before translation  Transcription factors turn genes “on”  These molecules either activate or repress gene products, such as mRNA

 Chromosomes in higher organisms are highly coiled around structural proteins called histones.  When genes are buried this way, RNA polymerase cannot get them to transcribe them into mRNA (so it has been essentially turned “off”)

 Enhancer- a section of DNA that increases the expression of a gene  Intron- the region on a gene that is transcribed into an mRNA molecule but not expressed in a protein.  Exon- the region of a gene that directly codes for a protein  It is the region of the gene that is expressed

 Transcription factors- molecules that work to either turn on or off the transcription eukaryotic genes  Histones- nuclear proteins that bind to the chromosomal DNA and condense it into highly packed coils

 Mammalian cells are more challenging to grow because they normally grow within multicellular organisms; they depend on other cells for products and stimuli. So a biotechnologist growing mammalian cells, must provide it with a substitute but right environment  Typically grown in broth cultures in fermenters  They have specific nutrients and special indicators

 Viruses infect organisms and are often the target of biotechnology therapies  Used as vectors to carry DNA between cells  Do not have cellular structure; collections of protein and nucleic acid molecules that become active once they are within a cell. Are tiny measure from 25 to 250nm  Viruses are either bacterial, plant or animal

 Viruses are classified further based on the specific type of cell infected an on other characteristics, such as genetic material and shape; they all have a thick protein coat surrounding a nucleic acid core of wither DNA or RNA  Lysogenic viruses incorporate their DNA in the host chromosome while lytic viruses do not  Viral vaccine molecules recognize specific viral surface proteins and target them for attack; protease inhibitors destroy proteases made by viruses in their attempts to take over host cells

 Viral DNA or RNA molecules are short so easy to manipulate, since they do not create as many proteins as cells do. Viral DNA is sometimes used as a vector because they can open to insert genes of interest.  Some companies are exploring the use of gene therapy to treat diabetes by replacing defective insulin genes in the pancreas  Gene therapy is possible treatment for cystic fibrosis and other genetic disorders