PinkMonkey Online Study Guide-Biology
CHAPTER 7 : CLASSICAL OR MENDELLIAN GENETICS
Definition : "Genetics is the study and understanding of the phenomena of heredity and variation."
The term ’genetics’ was first coined by Bateson in 1906. In Latin, it means genesis or origination of organisms.
Heredity is the transmission of characters
from one generation to the next, i.e., from parents to their offspring.
Because of heredity, the offspring resemble their parents. Heredity
is the essence of self-reproduction. It is owing to heredity or
self-reproduction that we commonly observe the phenomenon of "like
begets like", i.e., a seed of mango develops into a mango
tree, or the offspring of a dog is a puppy, and that of human beings
is a human being only.
Variations are the visible differences between
the parents and the offspring, or between two offsprings of the same parents.
An offspring receives all the characters from its parents and
yet, an offspring is never an exact copy of its parents. Similarly,
no two offsprings of the same parents are identical (exception : identical
In order to understand the principles of inheritance
and to discover the reasons for the variations, Mendel began a systematic
search during the second half of the nineteenth century. For this, Mendel
experimented on garden pea plants and performed various crosses with great
precision, care and objectivity. He carefully counted the plants resulting
from such crosses and kept statistical records of successive generations
with the accuracy of a mathematician.