Barr body

Examples of Barr body in the following topics:

• X-Inactivation

  • Early in development, when female mammalian embryos consist of just a few thousand cells (relative to trillions in the newborn), one X chromosome in each cell inactivates by tightly condensing into a quiescent (dormant) structure called a Barr body.
  • The chance that an X chromosome (maternally or paternally derived) is inactivated in each cell is random, but once the inactivation occurs, all cells derived from that single cell will have the same inactive X chromosome or Barr body.
  • The XXY genotype, corresponding to one type of Klinefelter syndrome, corresponds to phenotypically male individuals with small testes, enlarged breasts, and reduced body hair .
  • This can be seen as several Barr bodies in each cell nucleus.

• Virus Classification

  • The capsid of the (a) polio virus is naked icosahedral; (b) the Epstein-Barr virus capsid is enveloped icosahedral; (c) the mumps virus capsid is an enveloped helix; (d) the tobacco mosaic virus capsid is naked helical; and (e) the herpesvirus capsid is complex.

• Body Plans

  • Animal body plans can have varying degrees of symmetry and can be described as asymmetrical, bilateral, or radial.
  • Animal body plans follow set patterns related to symmetry.
  • In order to describe structures in the body of an animal it is necessary to have a system for describing the position of parts of the body in relation to other parts .
  • Animals exhibit different types of body symmetry.
  • The table illustrates common directional terms that are used to describe the position of body parts in relation to other body parts.

• The Role of the Circulatory System

  • The circulatory systems is a network of blood vessels supplying the body with oxygen and nutrients, while removing carbon dioxide and waste.
  • The circulatory system can be thought of as a highway system that runs throughout the body .
  • Made of specialized and unique cardiac muscle, it pumps blood throughout the body and to the heart itself.
  • Therefore, circulatory systems have had to evolve to accommodate the great diversity of body sizes and body types present among animals.
  • The heart is central to the human circulatory system, as it pumps blood throughout the body.

• Characteristics of the Animal Body

  • Every animal has a distinct body plan, adapted in response to environmental pressures, that limits its size and shape.
  • From a sponge to a worm to a goat, an organism has a distinct body plan that limits its size and shape.
  • The term body plan is the "blueprint" encompassing aspects such as symmetry, segmentation, and limb disposition.
  • However, there is also evidence of a more gradual development of body plans.
  • Animals' bodies are also designed to interact with their environments, whether in the deep sea, a rainforest canopy, or the desert.

• Spinal Cord

  • Connecting to the brainstem and extending down the body through the spinal column is the spinal cord: a thick bundle of nerve tissue that carries information about the body to the brain and from the brain to the body.
  • Grey matter is also composed of interneurons, which connect two neurons, each located in different parts of the body.
  • Axons and cell bodies in the dorsal (facing the back of the animal) spinal cord convey mostly sensory information from the body to the brain.
  • Axons and cell bodies in the ventral (facing the front of the animal) spinal cord primarily transmit signals controlling movement from the brain to the body.
  • One such treatment is to pump the body with cold saline to induce hypothermia.

• Animal Body Planes and Cavities

  • A sagittal plane divides the body into right and left portions.
  • Vertebrate animals have a number of defined body cavities .
  • The abdominopelvic cavity is the largest cavity in the body.
  • The midsagittal plane divides the body exactly in half into right and left portions.
  • Vertebrate animals have two major body cavities.

• Types of Skeletal Systems

  • A hydrostatic skeleton is one formed by a fluid-filled compartment within the body: the coelom.
  • For example, earthworms move by waves of muscular contractions (peristalsis) of the skeletal muscle of the body wall hydrostatic skeleton, which alternately shorten and lengthen the body.
  • Lengthening the body extends the anterior end of the organism.
  • Shortening the muscles then draws the posterior portion of the body forward.
  • They provide bodies with support, protection of organs, and aid in movement.

• Heat Conservation and Dissipation

  • Endotherms use their circulatory systems to help maintain body temperature.
  • For example, vasodilation brings more blood and heat to the body surface, facilitating radiation and evaporative heat loss, which helps to cool the body.
  • In cases of severe cold, a shivering reflex is activated that generates heat for the body.
  • Ecothermic animals use changes in their behavior to help regulate body temperature.
  • Describe some of the changes animals use in order to maintain body temperature

• Cells as the Basic Unit of Life

  • Like a brick wall, your body is composed of basic building blocks, and the building blocks of your body are cells.
  • Your body has many kinds of cells, each specialized for a specific purpose.
  • Just as a home is made from a variety of building materials, the human body is constructed from many cell types.
  • For example, epithelial cells protect the surface of the body and cover the organs and body cavities within.
  • Bone cells help to support and protect the body.