Genetics

Genetics is the study of heredity. It is appropriately regarded as the science that explains the similarities and differences between among the related organisms.

 

 

The blood theory of inheritance in human

People used to believe that the children received blood from their parents, and it was the union of blood that led to the blending of characteristics. That is how the terms 'blood relations' , 'blood will tell' and ' blood is thicker than water' came into existence. 

They are still used, despite the fact that blood is no more involved in inheritance. With the advances in Genetics, the more appropriate terms should be as follows

• Gene relations in place of blood relations
• Genes will tell instead of blood will tell

History

The blood theory of inheritance was questioned in 1850s, based on the fact that the semen contained no blood. Thus, blood was not being transferred to the offspring. Then the big question was what was the hereditary substance.

Development of Genetics

Mendel's experiments :  

In 1866, an Austrian monk named Gregor Johann Mendal, for the first time reported the fundamental laws of inheritance. He conducted several experiments on the breeding patterns of pea plants. Mendel put forth the theory of transmissible factors which states that inheritance is controlled by certain factors passed from parents to offsprings. His results were published in 1866 in an obscure journal Proceedings of the society of Natural sciences.

European botanists Correns and Hugo de Vries in 1900, independently and simultaneously rediscovered the theories of Mendel.

The year 1900 is important as it marks the begining the modern era of genetics.

 

 

Gene

In the early years of twentieth century, it was believed that the Mendel's  inheritance factors are very closely related to chromosomes of the cellls. In 1920s, the name gene was introduced by Willard Johannsen.

Chemical basis of inheritance

There was a controversy for quite sometime on the chemical basis of inheritance. There were two groups - the protein supporters and DNA supporters. It was in 1944, Avery and his associates presented convincing evidence that the chemical basis of heredity lies in DNA and not in protein. Thus, DNA was finally identified as the genetic material. Its structure was elucidated in 1952 by Watson and Crick.

Importance of genes in inheritance

Studies on twins

Monozygotic or identical twins contain the same genetic material. Studies conducted on identical twins make starting revelations with regard to inheritance. 

Oskar stohr and Jack Yufe were identical twins separated at birth. Oskar was taken to Germany where he was brought up his grandmother as a chiristian. Jack was raised by his father in Israel as a Jew. The two brothers were reunited at the age of 47. Despite the different environmental influences, their behavioural patterns and personalities were remarkably similar

• Both men had moustaches, wore two pocket shirts, and wire-rimmed glasses.
• Both loved spicy foods and tended to fall asleep in front of television.
• Both flushed the toilet before using.
• Both read magazines from back to front.
• Both stored rubber bands on their wrists.
• Both liked to sneeze in a room of strangers.

Besides Oskar and Jack, many other studies conducted on identical twins point out the importance of genes on the inherited characters related to personality and mannerisms.