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October, 2006
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Visualizing Soil Microorganisms via the Contact Slide Assay and Microscopy

JoVE 10053

Source: Laboratories of Dr. Ian Pepper and Dr. Charles Gerba - Arizona University
Demonstrating Author: Bradley Schmitz

Soil comprises the thin layer at the earth’s surface, containing biotic and abiotic factors that contribute to life. The abiotic portion includes inorganic particles ranging in size and shape that determine…

 Environmental Microbiology

Water Quality Analysis via Indicator Organisms

JoVE 10025

Source: Laboratories of Dr. Ian Pepper and Dr. Charles Gerba - Arizona University
Demonstrating Author: Luisa Ikner

Water quality analysis monitors anthropogenic influences such as pollutants, nutrients, pathogens, and any other constituent that can impact the water’s integrity as a resource. Fecal contamination contributes…

 Environmental Microbiology

The TUNEL Assay

JoVE 5651

One of the hallmarks of apoptosis is the nuclear DNA fragmentation by nucleases. These enzymes are activated by caspases, the family of proteins that execute the cell death program. TUNEL assay is a method that takes advantage of this feature to detect apoptotic cells. In this assay, an enzyme called terminal deoxynucleotidyl transferase catalyzes the addition of dUTP…

 Cell Biology

An Overview of Genetic Engineering

JoVE 5552

Genetic engineering – the process of purposefully altering an organism’s DNA – has been used to create powerful research tools and model organisms, and has also seen many agricultural applications. However, in order to engineer traits to tackle complex agricultural problems such as stress tolerance, or to realize the promise of gene therapy for treating…


C. elegans Maintenance

JoVE 5104

Ceanorhabditis elegans has been, and is still, used to great success as a model organism for studying a variety of developmental, genetic, molecular and even physical phenomena. In order to use C. elegans to its full potential, proper care and attention to the basic maintenance of this powerful organism is essential.

In this video you will learn the basic…

 Biology I

Introduction to the Bunsen Burner

JoVE 5035

The Bunsen burner, named after and co-designed by Robert Bunsen in 1854, is a common laboratory instrument that produces a hot, sootless, non-luminous flame. The Bunsen Burner allows for precise regulation of the mixing of gas and oxygen in its central barrel before combustion, which ignites the flame. By manipulating the Bunsen burner, both the size and temperature of the …

 General Laboratory Techniques

Genetics of Speciation

JoVE 11126

Speciation is the evolutionary process resulting in the formation of new, distinct species—groups of reproductively isolated populations.

The genetics of speciation involves the different traits or isolating mechanisms preventing gene exchange, leading to reproductive isolation. Reproductive isolation can be due to reproductive barriers that have effects either before or after the formation of a zygote. Pre-zygotic mechanisms prevent fertilization from occurring, and post-zygotic mechanisms reduce the viability, or reproductive capacity, of the hybrid offspring. For example, pre-zygotic mechanisms act early in the life cycle of an organism, imposing the strongest impediment to gene flow, and preventing unfavorable mating combinations. Some mating combinations produce hybrid individuals. Natural selection can work against the production of hybrids with low fitness, thereby increasing reproductive isolation between two species. Post-zygotic reproductive barriers can be due to the intrinsic inviability of hybrids. Genetic complications resulting from aberrant ploidy levels, different chromosomal arrangements, or gene incompatibilities where the alleles do not function properly contribute to different genetic makeup and alternative developmental pathways in hybrids. These genetic alterations affect both plants and animals, leading to post-zygoti

 Core: Biology

Plant Breeding and Biotechnology

JoVE 11113

Crop cultivation has a long history in human civilization, with records showing the cultivation of cereal plants beginning at around 8000 BC. This early plant breeding was developed primarily to provide a steady supply of food.

As humans' understanding of genetics advanced, improved crop varieties could be achieved more quickly. Artificial selection could be more directed, and crop varieties enhanced for favorable traits more quickly to produce better, more robust, or more palatable plants. However, traditional techniques for breeding plants are slow and do not always produce the desired crop varieties. Later, biotechnological tools made it easier to engineer desired traits into plants that are otherwise difficult to breed using traditional methods. For example, improving nutritional deficiency in plants is difficult via artificial selection, and particularly challenging for vitamin A and iron. Rice, for example, does not contain genes for beta carotene, which is a vitamin A precursor. However, it does contain genes for the compound geranylgeranyl pyrophosphate, which can be sequentially converted to beta carotene using four enzymes. Rice was engineered using genes for two enzymes derived from daffodils, and the remaining two enzymes from the bacteria Erwinia uredovora. The resulting crop is known as golden rice. Because rice is the staple food o

 Core: Biology

What is Cell Signaling?

JoVE 10985

Despite the protective membrane that separates a cell from the environment, cells need the ability to detect and respond to environmental changes. Additionally, cells often need to communicate with one another. Unicellular and multicellular organisms use a variety of cell signaling mechanisms to communicate to respond to the environment.

Cells respond to many types of information, often through receptor proteins positioned on the membrane. For example, skin cells respond to and transmit touch information, while photoreceptors in the retina can detect light. Most cells, however, have evolved to respond to chemical signals, including hormones, neurotransmitters, and many other types of signaling molecules. Cells can even coordinate different responses elicited by the same signaling molecule. Typically, cell signaling involves three steps: (1) reception of the signal, (2) signal transduction, and (3) a response. In most signal reception, a membrane-impermeable molecule, or ligand, causes a change in a membrane receptor; however, some signaling molecules, such as hormones, can traverse the membrane to reach their internal receptors. The membrane receptor can then send this signal to intracellular messengers, which transduces the message into a cellular response. This intracellular response may include a change transcription, translation, protein activation,

 Core: Biology

Humoral Immune Responses

JoVE 10897

The humoral immune response, also known as the antibody-mediated immune response, targets pathogens circulating in “humors,” or extracellular fluids, such as blood and lymph. Antibodies target invading pathogens for destruction via multiple defense mechanisms, including neutralization, opsonization, and activation of the complement system. Patients that are impaired in the production of antibodies suffer from severe and frequent infections by common pathogens and unusual pathogens. B lymphocytes, also called B cells, detect pathogens in the blood or lymph system. Although B cells originate in the bone marrow, their name is derived from a specialized organ in birds in which B cells were first discovered, the bursa of Fabricius. After release from the bone marrow, B cells mature in secondary lymphoid tissues, such as the spleen, lymph nodes, tonsils and mucosa-associated lymphoid tissue throughout the body. B cells bind to specific parts of a pathogen, called antigens, via their B cell receptors. In addition to antigen binding, B cells require a second signal for activation. This signal can be provided by helper T cells or, in some cases, by the antigen itself. When both stimuli are present, B cells form germinal centers, where they proliferate into plasma cells and memory B cells. All cells that are derived from a common ancestral B c

 Core: Biology
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