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Melanins: Insoluble polymers of Tyrosine derivatives found in and causing darkness in skin (Skin pigmentation), hair, and feathers providing protection against Sunburn induced by Sunlight. Carotenes contribute yellow and red coloration.

Genetic Drift

JoVE 11128

Natural selection—probably the most well-known evolutionary mechanism—increases the prevalence of traits that enhance survival and reproduction. However, evolution does not merely propagate favorable traits, nor does it always benefit populations.

Life is not fair. A deer grazing contentedly in a field can have her meal cut tragically short by a bolt of lightning. If the doomed doe is one of only three in the population, 1/3 of the population’s gene pool is lost. Random events like this can indelibly affect a population, sometimes for generations. This evolutionary mechanism is called genetic drift. Genetic drift is a shift in population allele frequencies due to chance events. Alleles are variations of a gene, and their frequency is the portion, or percentage, of the population with that allele. Genetic drift can alter the frequencies of advantageous, neutral, and harmful alleles alike. Genetic drift does not dramatically impact sufficiently large populations; this is because it does not occur in isolation, but alongside other evolutionary mechanisms, like natural selection. In large populations, many individuals can be lost, and the remaining gene pool is still diverse enough for natural selection to act. However, genetic drift can sharply reduce genetic diversity in small populations, creating a sampling error. A sampl

 Core: Biology

Hardy-Weinberg & Genetic Drift- Concept

JoVE 10559

Evolutionary change is interesting and important to study, but changes in populations occur over long periods of time and in huge physical spaces and are therefore very difficult to measure. In general, studying phenomena like this requires the use of mathematical models which are built using parameters that can be conveniently measured. These models are then used to make predictions about how …

 Lab Bio

Compound Administration II

JoVE 10388

Source: Kay Stewart, RVT, RLATG, CMAR; Valerie A. Schroeder, RVT, RLATG. University of Notre Dame, IN



Compound administration is often an integral component of an animal study. Many factors need to be evaluated to ensure that the compound is delivered correctly. The route of administration affects the mechanisms of…

 Lab Animal Research

Zebrafish Breeding and Embryo Handling

JoVE 5150

Zebrafish (Danio rerio) are an important model organism that is particularly valuable for research in developmental biology. Zebrafish are extremely fertile and can produce hundreds of progeny per week, so it is relatively easy to collect a large number of embryos for high sample numbers. Furthermore, zebrafish undergo rapid development and embryos are transparent, allowing for easy…

 Biology II

An Introduction to the Zebrafish: Danio rerio

JoVE 5128

Zebrafish (Danio rerio) are small freshwater fish that are used as model organisms for biomedical research. The many strengths of these fish include their high degree of genetic conservation with humans and their simple, inexpensive maintenance. Additionally, gene expression can be easily manipulated in zebrafish embryos, and their transparency allows for observation of developmental…

 Biology II

Technical Aspect of the Automated Synthesis and Real-Time Kinetic Evaluation of [11C]SNAP-7941

1Department of Biomedical Imaging and Image-guided Therapy, Division of Nuclear Medicine, Medical University of Vienna, 2Department for Pharmaceutical Technology and Biopharmaceutics, Faculty of Life Sciences, University of Vienna, 3Ludwig Boltzmann Institute Applied Diagnostics, 4CBmed GmbH - Center for Biomarker Research in Medicine

JoVE 59557

 Chemistry

Flat Mount Imaging of Mouse Skin and Its Application to the Analysis of Hair Follicle Patterning and Sensory Axon Morphology

1Department of Molecular Biology and Genetics, Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, 2Department of Neuroscience, Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, 3Department of Ophthalmology, Howard Hughes Medical Institute, Johns Hopkins University School of Medicine

JoVE 51749

 Neuroscience

Agarose-based Tissue Mimicking Optical Phantoms for Diffuse Reflectance Spectroscopy

1Graduate School of Bio-application & Systems Engineering, Tokyo University of Agriculture & Technology, 2Department of Mechanical Engineering, Kushiro National College of Technology, 3Division of Bioinformation and Therapeutic Systems, National Defense Medical College Research Institute, 4Graduate School of Science and Engineering, Yamagata University, 5College of Design and Manufacturing Technology, Muroran Institute of Technology, 6Department of Livestock Services, Ministry of Fisheries and Livestock, Government of Bangladesh

JoVE 57578

 Bioengineering
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