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from article Zoonoses
The Rocky Mountain wood tick (Dermacentor andersoni) is the etiologic agent of Rocky Mountain spotted fever. (Credit: Christopher Paddock/Centers for Disease Control and Prevention)
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from article Zoonoses
Cryptococcosis of a lung in a patient with acquired immune deficiency syndrome (AIDS). Histopathology of the lung shows a widened alveolar septum containing a few inflammatory cells and numerous yeasts of Cryptococcus neoformans. The inner layer of…
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from article Zoonoses
Light micrograph of a dog roundworm (Toxocara canis). (Credit: olgaru79/Shutterstock)
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from article Background extinction
Fossilized trilobite, an extinct marine arthropod, from Morocco, North Africa. Many orders of trilobites were eliminated by background extinction over 270 million years before the mass extinction at the end of the Permian period finished them.…
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from article Archeology
Exterior view of the entrances to two small Neolithic passage graves at Knowth, County Meath, Ireland, which date to approximately 3200 BCE. Graves of this type help archeologists to reconstruct past lifeways of the humans that created them.…
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from article Archeology
Stone tools from one of the oldest archeological sites in the world, OGS7 at Gona in Ethiopia, dating to 2.6 million years ago. (Top left) Refitting of flakes to a core (modified cobblestones that have been flaked). There are a variety of artifacts,…
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from article Archeology
Stonehenge monument in Wiltshire, England. The first stones to be raised at this site have been dated to about 2500 BCE. The archeological evidence supports the theory that this sophisticated prehistoric stone circle was used as a ceremonial burial…
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from article Green fluorescent protein
A hippocampal neuron filled with green fluorescent protein (GFP) and labeled for presynaptic (blue) and postsynaptic (red) structures. (Courtesy of Philip Buttery, Department of Clinical Neurosciences, University of Cambridge, UK)
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from article Alkaloid
Solanine is a poisonous glycoalkaloid found in highest concentration in green-discolored potatoes. (Credit: Yuelan/Getty Images)
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from article Fungal genetics
Three different kinds of reproduction occurring in fungi, each of which provides opportunities for genetic analysis. (a) Sexual reproduction leads to recombination (R) of genes at meiosis. (b) Asexual reproduction (shown here in a typical haploid…
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from article Fungal genetics
Genetic crossing-over at the molecular level. As part of the process, heteroduplex DNA is formed (center). If the heteroduplex is corrected, as shown here from a to A, gene conversion is explained. Either or both heteroduplexes can be converted to A…
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from article Multiple sclerosis
A section of the brain contains several opaque, vaguely gelatinous areas in the white matter. These areas are typical of multiple sclerosis and represent regions of demyelination, also known as plaques (indicated by arrows). The plaques are…
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from article Multiple sclerosis
Photomicrograph of an inactive plaque. Gray matter is seen in the upper left corner of this image. The adjacent purple band shows normally staining white matter. However, the remainder of the image (right lower half) shows white matter that is…
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from article Chlamydia
Human pap smear showing Chlamydia trachomatis in the vacuoles. Colorization was done with hematoxylin and eosin stain. (Credit: Lance Liotta/National Cancer Institute, National Institutes of Health)
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from article Central nervous system
The brain and spinal cord (both shown in green color) constitute the central nervous system of the human body. (Copyright © McGraw-Hill Education)
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from article Transformation (bacteria)
Steps involved in bacterial transformation: a donor bacterium undergoes cell lysis, releasing its naked DNA; a recipient bacterium takes up the DNA; and then transformation (recombination) occurs.
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from article Intron
Proposed generation of mosaic proteins for sponge receptor tyrosine kinase (RTK). The gene coding for a donor protein d-P, which consists of an Ig-like domain [phase I], undergoes modularization [phase II] by insertion of introns (In). One of the…
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from article Polymerase chain reaction (PCR)
The exponential increase in the amount of DNA after each PCR cycle. (Credit: McGraw-Hill Education)
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from article Polymerase chain reaction (PCR)
The PCR cycle and the mechanism of DNA synthesis.
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from article Albumin
Human serum albumin. (a) Domain structure of the defatted protein and (b) location of eight myristic acid (a 14-carbon fatty acid) ligands in different binding sites. In a, the secondary structure of the protein is shown schematically, and the…
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from article Embryonic induction
Experimental demonstration of primary embryonic induction in amphibian embryo. (a) Mesoderm tissue surrounding dorsal lip of donor embryo was grafted to (b) ventral side of pigmented host embryo. (c) External development of host reveals two neural…
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from article Neuroimmunology
Hypothalamic-pituitary-adrenal axis of neuroimmune interaction.
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from article Bioluminescence
Bioluminous crystal jellyfish (Aequorea victoria). (Copyright © Lisa Werner/Alamy Stock Photo)
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from article Neural crest
Stages of neural crest development. Transverse sections through typical vertebrate embryo ectodermal layer during early development. (a) The ectodermal layer, which started as a uniform sheet, becomes subdivided into three zones. The neural plate…
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from article Neural crest
Evolution of neural crest and vertebrate traits. Both jawed and jawless vertebrates have the neural crest, while other chordates (animals that have, for at least part of the life cycle, a notochord) do not. (Modeled after B. K. Hall, The Neural…
