Heredity and Variation

HEREDITY AND VARIATION    

Introduction

- Genetics is a branch of biology that focuses on the inheritance and variation of traits from parents to offspring. 

- Inheritance is the process through which characteristics are passed from parents to their progeny, forming the basis of heredity. 

- Variation refers to the extent to which offspring differ from their parents in terms of traits. 

- Humans have understood the role of sexual reproduction in generating variation since ancient times, dating back to 8000-1000 B.C. 

- Early humans harnessed naturally occurring variations in wild plant and animal populations for selective breeding to obtain organisms with desirable traits.

 - One example of this selective breeding is the development of Indian breeds of cows, such as Sahiwal cows in Punjab. 

- It's important to note that our ancestors had limited scientific understanding of the mechanisms underlying inheritance and variation.

 Mendel's law of inheritance

- In the mid-nineteenth century, Gregor Mendel conducted groundbreaking experiments on garden peas (1856-1863) that led to the understanding of inheritance in living organisms. 

- Mendel's experiments marked the first application of statistical analysis and mathematical logic to biological problems, bringing a scientific approach to genetics. 

- Mendel's extensive sampling size and rigorous experimentation methods lent credibility to his findings. 

- Mendel's work demonstrated general rules of inheritance, rather than mere conjecture, by confirming his inferences across successive generations of pea plants. 

- He focused on traits with two opposing forms, such as tall or dwarf plants and yellow or green seeds, which allowed him to establish a foundational framework for inheritance. 

- Mendel's experiments involved artificial pollination and cross-breeding using true-breeding pea lines. True-breeding lines exhibited stable trait inheritance over multiple generations.

 - He selected 14 true-breeding pea plant pairs, each differing in one contrasting trait, such as smooth vs. wrinkled seeds, yellow vs. green seeds, inflated vs. constricted pods, and tall vs. dwarf plants.