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Cellular Defects - Osteoblasts, Osteoclasts and Osteocytes

By: HWC, Views: 7390

■ Metabolically active bone-building cells that secrete astroid. ■ Cover surfaces of newly formed bone and respond to growth stimuli ■ Less responsive to growth factors as the body ages. ■ Contribute to hone loss once their reproductive and biosynthetic potential lessens....

Activation Energy - Valence Electrons

By: HWC, Views: 7259

■ Shared electrons in the outermost orbital form bonds. These electrons are called valence electrons. ■ Valence electrons are disrupted and can be rearranged into a new bond. ■ The energy necessary to start a reaction and break bonds is called the activation energy. ■ Reactants have...

A timeline of the teeth (Explained - No Audio)

By: HWC, Views: 6707

Although most babies don't appear to have any teeth when they are born, they are in fact already well developed out of sight beneath the gum. The first molars erupt at about 12-14 months. The canines follow at about 16-18 months . By 3 years old, the second molars have usually erupted, c...

Oral Hygiene & Braces Animation

By: HWC, Views: 7284

Caring for Your Retainer Retainers, just like your teeth collect plaque, bacteria and food particles. You should clean your retainer everyday! Keep your retainer soaking when it is not in your mouth. Use a mouthwash rinse to freshen it up and keep it free of bacteria. Keep your retainer away fr...

Stages of Mitosis - Prophase, Prometaphase, Metaphase, Anaphase & Telophase

By: HWC, Views: 7497

In mitosis, the nucleus divides to produce two nuclei that are genetically identical to each other and to the parent nucleus. To prepare for division, the DNA replicates in the preceding interphase. Although the chromosomes are not yet compacted and visible as discrete bodies, we illustrate them ...

DNA Sequences - Dideoxy Sequencing

By: HWC, Views: 7107

A short, radiolabeled primer is annealed to the single-stranded DNA to be sequenced. The DNA serves as a template for in vitro DNA synthesis. The DNA-primer mixture is split into four separate tubes. DNA polymerase and a solution of dNTPs are added to each tube. One of the four 2',3' dideoxy-N...

Hierarchical Sequencing Method - Sequence Tagged Sites

By: HWC, Views: 7031

In the hierarchical sequencing method, researchers begin by collecting cells. In humans, each cell contains 23 pairs of chromo-somes. Here we specifically track the DNA from just one of the 23 pairs. Chromosomes have a series of unique DNA sequences, called sequence-tagged sites (STSs), that a...

Plant Defense Mechanisms from Pathogens

By: HWC, Views: 7256

Plants and pathogens have coevolved such that pathogens can recognize plants by the sugars, or other molecules, they produce. Plants, in turn, can recognize pathogens by the molecules they produce. The ability to recognize pathogens allows plants to activate defense systems that can prevent wides...

Phases of an Action Potential - Resting Potential, Threshold, Rising, Falling, & Recovery Phases

By: HWC, Views: 7201

In this tutorial, we will review the phases of an action potential measured from a small area of a neuron's membrane. The action potential can be divided into five phases: the resting potential, threshold, the rising phase, the falling phase, and the recovery phase. When the neuron is at rest,...