physical map

Examples of physical map in the following topics:

• Physical Maps and Integration with Genetic Maps

  • Physical maps display the physical distance between genes and can be constructed using cytogenetic, radiation hybrid, or sequence mapping.
  • A physical map provides detail of the actual physical distance between genetic markers, as well as the number of nucleotides.
  • There are three methods used to create a physical map: cytogenetic mapping, radiation hybrid mapping, and sequence mapping.
  • Genetic maps provide the outline and physical maps provide the details.
  • Describe the methods used to physically map genes: cytogenetic mapping, radiation hybrid mapping, and sequence mapping

• Genetic Maps

  • Shortly after Gregor Mendel (the father of modern genetics) proposed that traits were determined by what are now known as genes, other researchers observed that different traits were often inherited together and, thereby, deduced that the genes were physically linked by being located on the same chromosome.
  • The mapping of genes relative to each other based on linkage analysis led to the development of the first genetic maps.
  • The generation of genetic maps requires markers, just as a road map requires landmarks (such as rivers and mountains).
  • Early genetic maps were based on the use of known genes as markers.
  • Because genetic maps rely completely on the natural process of recombination, mapping is affected by natural increases or decreases in the level of recombination in any given area of the genome.

• Genetic Linkage and Distances

  • Morgan identified a 1:1 ratio between a segregating trait and the X chromosome, suggesting that the random segregation of chromosomes was the physical basis of Mendel's model.
  • He suggested that alleles become unlinked when chromosomes physically exchange segments.
  • When synapsed, homologous chromosomes undergo reciprocal physical exchanges of DNA at their arms in a process called homologous recombination, or more simply, "crossing over."
  • Sturtevant divided his genetic map into map units, or centimorgans (cM), in which a recombination frequency of 0.01 corresponds to 1 cM.
  • This genetic map orders Drosophila genes on the basis of recombination frequency.

• Cognitive Learning and Sociobiology

  • In addition to visual processing, cognitive learning is also enhanced by remembering past experiences, touching physical objects, hearing sounds, tasting food, and a variety of other sensory-based inputs.
  • Tolman proved a decade later that the rats were making a representation of the maze in their minds, which he called a "cognitive map."

• Genetic Linkage and Violation of the Law of Independent Assortment

  • The segregation of alleles into gametes can be influenced by linkage, in which genes that are located physically close to each other on the same chromosome are more likely to be inherited as a pair.
  • Using this information, they have constructed elaborate maps of genes on chromosomes for well-studied organisms, including humans.

• Biotechnology

  • Just as information technology has led to Google maps that enable people to get detailed information about locations around the globe, genomic information is used to create similar maps of the DNA of different organisms .
  • These findings have helped anthropologists to better understand human migration and have aided the field of medicine through the mapping of human genetic diseases.
  • In genomics, the DNA of different organisms is compared, enabling scientists to create maps with which to navigate the DNA of different organisms.

• Tastes and Odors

  • Recent evidence suggests that taste receptors are uniformly distributed across the tongue; thus, the traditional tongue map is no longer valid.
  • Uniform distribution of taste receptors (the myth of the tongue map)
  • Recent evidence suggests that taste receptors are uniformly distributed across the tongue; thus, this traditional tongue map is no longer valid.

• Cell Signaling and Cell Growth

  • Activation of RTKs initiates a signaling pathway that includes a G-protein called RAS, which activates the MAP kinase pathway described earlier.
  • The enzyme MAP kinase then stimulates the expression of proteins that interact with other cellular components to initiate cell division.

• Brain: Cerebral Cortex and Brain Lobes

  • Areas within the motor cortex map to different muscle groups; there is some organization to this map .
  • The parietal lobe contains a somatosensory map of the body similar to the motor cortex.

• Physical and Chemical Barriers

  • The innate immune response has physical and chemical barriers that exist as the first line of defense against infectious pathogens.
  • Some pathogens have evolved specific mechanisms that allow them to overcome physical and chemical barriers.