NEET BIOLOGY BY SHASHI SIR

  6.10 DNA FINGERPRINTING   DNA fingerprinting is a very quick way to compare the DNA sequences of any two individuals. DNA fingerprinting involves identifying differences in some specific regions in DNA sequence called as repetitive DNA, because in these sequences, a small stretch of DNA (TANDEM REPEATS) is repeated many times.  Satellite DNA Repetitive DNA are separated from bulk genomic DNA as different peaks during density gradient centrifugation.  The bulk DNA forms a major peak and the other small peaks are referred to as satellite DNA. Depending on base composition (A : T rich or G:C rich), length of segment, and number of repetitive units, the satellite DNA is classified into many categories, such as micro-satellites, mini-satellites etc.                                 POLYMORPHISM  &  POLYMORPHIC DNA  Polymorphism is a variation at genetic...

  Regulation of Breathing The regulation of breathing is based in the body's acid/base balance. The Central Chemoreceptors (CCR), primarily responsible for the breathing stimulation, are affected by the PaCO 2.  The responsiveness of the peripheral receptors is tied to the level of pH and PaCO 2 . Together these provide the ultimate in servo-control - sensors provide feedback that increase or decrease breathing. Medullary Respiratory Center The rhythmic cycle of breathing originates in the medulla. Higher brain centers (voluntary control), systemic receptors, and reflexes modify the medulla's output. However, no truly separate inspiratory and expiratory centers have been identified. The medulla does contain several widely dispersed groups of respiratory-related neurons that form dorsal and ventral respiratory groups. Fig-Schematic illustration of the respiratory components of the lower brainstem (pons and medulla oblongata). PNC = pneumotaxic center; APC = apneustic center; DR...