Biotech Chapter 4

Introduction to Studying DNA

• DNA is central to biotechnology research and development
• This chapter covers the structure and function of DNA
• It explains how DNA encodes proteins and how molecular modeling is used to study these processes.
• It differentiates between eukaryotic and prokaryotic chromosomes and how this impacts gene regulation
• The process of growing bacterial cultures in liquid and solid media
• A discussion on viruses and their role in genetic engineering
• The fundamental process of genetic engineering, including recombinant DNA technology, site-specific mutagenesis, and gene therapy
• Gel electrophoresis and how molecular characteristics affect their migration
• The structure of DNA reveals that is composed of nucleotides
• Nucleotides have a sugar molecule, phosphate group and nitrogenous bases
• The two strands of DNA run antiparallel, meaning they run in opposite directions.
• The bases on the two strands are joined together through H-bonds which are weak and break easily when exposed to high temperatures or chemical treatments.
• The amount of adenine equals the amount of thymine; the amount of guanine equals the amount of cytosine
• DNA replicates in a semiconservative fashion.

DNA Structure and Function

• Proteins are produced when genes are transcribed into mRNA then translated into the protein code
• This is called "gene expression."

DNA Structure: Nucleotide Chains in a Double Helix

• Two chains of nucleotides form a double helix
• Nucleotides are connected via hydrogen bonds
• Each nucleotide contains a sugar molecule, a phosphate group, and a nitrogenous base.

DNA Structure: Nitrogenous Bases

• Nucleotides contain adenine, thymine, guanine, and cytosine
• Adenine pairs with thymine
• Guanine pairs with cytosine

DNA Structure: Antiparallel Strands

• The nucleotides in one strand face one direction, while those in the other strand face the opposite direction.
• This is called "antiparallel."
• Hydrogen bonds holding the antiparallel strands together are relatively weak.
• This allows the strands to easily separate for replication or transcription.

Similarities in DNA Molecules Among Organisms

• DNA is composed of four nucleic monomers
• Virtually all DNA molecules form a double helix
• The amount of adenine equals the amount of thymine, and the amount of guanine equals the amount of cytosine
• The orientation of nucleotides in each strand is opposite to the other
• DNA undergoes semiconservative replication

DNA Replication

• Replication is a semiconservative process, where each parent strand is conserved in the next generation
• This means new DNA molecules are formed with one original strand and one new strand

Variations in DNA Molecules

• The number of DNA strands in an organism varies
• DNA length in base pairs also varies
• Organisms vary in the number and type of genes, as well as noncoding regions.
• The shape of DNA strands varies among organisms.
• A single, circular DNA molecule is found in bacteria.

Section 4.1 Vocabulary

• Key terms are defined with descriptions

Section 4.2 Sources of DNA

• DNA is naturally produced in cells
• DNA can be isolated from cells and cultures
• Bacterial operon is an important structure
• The controlling elements turn genetic expression ON and OFF.

Bacterial Cell Culture

• Scientists provide an environment or medium for bacterial growth
• Some bacteria grow in liquid media, such as broth.
• Also in solid media, like agar.

Eukaryotic DNA

• Eukaryotic genes have a promoter region where RNA polymerase binds to start transcription
• Transcription factors may bind at enhancer regions and increase gene expression

Mammalian Cell Culture

• Growing mammalian cells requires more complex conditions than bacterial cells
• Mammalian cells are typically grown in a broth culture.

Viral DNA

• Viruses are collections of protein and nucleic acid molecules
• They become active when inside a cell
• Viruses are classified according to the type of cell they attack (bacterial, plant, or animal)

Section 4.2 Vocabulary

• Definitions of key terms related to DNA isolation

Section 4.3 Isolating and Manipulating DNA

• Genetic engineering modifies DNA to alter protein production
• The process involves identifying a target molecule, isolating instructions, manipulating DNA, and harvesting the product.

Recombinant DNA Technology

• Methods to create new DNA molecules

Site-Specific Mutagenesis

• A technique to change the genetic code in specific sections of DNA

Gene Therapy

• A process to correct faulty DNA, addressing genetic diseases and disorders

Section 4.4 Using Gel Electrophoresis to Study Gene Molecules

• Electrophoresis separates molecules based on size, shape, and charge, using an electric field.
• Agarose is often used as a medium in electrophoresis
• Components of electrophoresis include agarose solution, electrophoresis buffer, Electrophoresis gel box, Power supply, Visualization system
• Agarose gels have differing concentrations
• PCR products are separated based on size, using electrophoresis.

DNA Gel Stains

• Nucleic acids are colorless, so DNA must be stained to be visible.
• Ethidium bromide (EtBr) is frequently used, but other stains are often preferred due to safety concerns
• EtBr glows orange in the presence of DNA when exposed to UV light.

DNA Samples on a Gel

• Gel electrophoresis is used to separate different DNA fragments
• DNA samples are loaded into wells, and then subjected to an electric field and separated by size

Section 4.4 Vocabulary

• Defines terms related to gel electrophoresis