Introduction of Principles of Inheritance and Variation

Introduction of Principles of Inheritance and Variation:

Why an elephant always gives birth only to a baby elephant and not some other animal? Or why a mango seed forms only a mango plant and not any other plant? Given that they do, are the offspring identical to their parents? Or do they show differences in some of their characteristics? Have you ever wondered why siblings sometimes look so similar to each other? Or sometimes even so different?

• Humans knew from as early as 8000-1000 B.C. that one of the causes of variation was hidden in sexual reproduction.             
• They used natural variances in plant and animal populations to selectively breed and select for creatures with desirable characteristics. E.g., Sahiwal cows in Punjab.
• Genetics: Genetics deals with the inheritance, as well as the variation of characters from parents to offspring. Under genetics, both heredity and variations are studied together.
  

1. Gene is the basic unit of inheritance and is located on chromosomes.  
2. Gregor Johann Mendel is known as - the ‘Father of Genetics’. He proposed 3 main laws which are known as Mendel’s laws. 
3. The Father of modern genetics is William Bateson
4. The Father of Human Genetics: Archibald Garrod 
5. The Father of experimental genetics: Thomas Hunt Morgan

• Inheritance: Inheritance is the process by which characters are passed on from parent to progeny, which forms the basis of heredity.
• Heredity: Heredity is a process of transmission of traits from parents to their offspring either via sexual reproduction. These characteristics or traits are located on the chromosomes in the form of genes. 
• Variation: Variation is the degree by which progeny differ from their parents. Variations in the characters of offspring arise due to a unique process called genetic recombination during crossing-over events of meiosis.