The MHC has been divided into three regions on the basis of structure, function and alloreactivity of the gene products, which-are: 1. Class - I at the telomeric ends 2. Class - II at the centromeric ends 3. Class - III, which is located between class - I and II regions. The classic class I and II genes code for [...]
In this article we will discuss about the Mendel's tri-hybrid and multi-hybrid crosses. Mendel extended his observations to tri-hybrid crosses involving three pairs of contrasting characters. The characters he considered were: seed shape—smooth (S) vs. wrinkled (s); colour of cotyledons—yellow (Y) vs. green (y); and flower colour—violet (V) vs. white (v). The F1 hybrid produces 8 types of gametes. These [...]
In this article we will discuss about the role of environment in changing the form and degree of expression of some genes resulting in a corresponding change in the phenotype. Penetrance and Expressivity: The presence of a gene does not always bear an absolute relationship with the appearance or absence of a trait. In the ABO blood group system, the [...]