HEREDITY AND INHERITANCE

 INHERITANCE FROM THE PREVIOUS GENERATION GIVES BOTH A COMMON BASIC BODY ORGANISATION, AS WELL AS SUBTLE CHANGES IN IT, FOR THE NEXT GENERATION. IF ONE BACTERIUM DIVIDES AND THEN THE PRODUCED TWO BACTERIA DIVIDE AGAIN , THE FOUR INDIVIDUAL BACTERIA PRODUCED WOULD VERY IDENTICAL. THERE WOULD BE ONLY VERY MINOR CHANGES BETWEEN  THEM ,GENERATED DUE TO SMALL INACCURACIES IN DNA COPYING. IF REPRODUCTION IS SEXUAL, EVEN GREATER DIVERSITY WILL BE CREATED. 

HEREDITY -

                  THE MOST OBVIOUS RESULT OF THE REPRODUCTIVE PROCESS STILL REMAINS THE GENERATION OF INDIVIDUALS OF SIMILAR DESIGN. THE RULE OF HEREDITY ENSURE THE PROCESS BY WHICH CHARACTERISTICS AND TRAITS ARE RELIABLY INHERITED.

 

RULES FOR THE INHERITANCE OF TRAITS :

   MENDEL CONTRIBUTIONS -

                                                    THE RULES OF THE INHERITANCE OF THESE TRAITS  IN HUMANS ARE RELATED TO THE FACT THAT BOTH THE MOTHER AND FATHER GIVE PRACTICALLY EQUAL AMOUNTS GENETIC MATERIAL TO THE CHILD. THIS SHOW THAT EACH TRAIT CAN BE INFLUENCED BY BOTH MATERNAL AND PATERNAL DNA. THUS FOR EACH TRAIT THERE WILL BE TO DIFFERENT VERSIONS IN EACH CHILD. MENDEL USED VARIOUS CONTRASTING VISIBLE CHARACTERS OF GARDEN PEAS -ROUND SEEDS,SHORT/TALL PLANT AND SO ON. HE TOOK PEA PLANT WITH SEPARATE CHARACTERISTICS , SAY, A TALL PLANT, GENERATED PROGENY FROM THEM, CALCULATED THE PERCENTAGE OF SHORT OR TALL PROGENY.

 

IN THE FIRST PLACE, THERE WAS NO MEDIAN CHARACTERISTICS IN THE FIRST GENERATION, OR F1 ,   PROGENY NO MEDIUM HEIGHT PLANTS. ALL PLANT PRODUCED WERE TALL. THIS INDICATED THAT ONLY ONE OF THE PARENTAL TRAITS WAS OBSERVED, NOT SOME MIXTURE OF THE TWO. PARENTAL TALL PLANT AND THESE F1 TALL PLANT TO REPRODUCE BY SELF POLLINATION. THE PROGENY OF THE PARENTAL TALL PLANTS ARE ALL TALL. THE F2 OR SECOND GENERATION, PROGENY OF THE F1 TALL PLANTS ARE NOT TALL. THIS SHOWS THE BOTH OF SHORTNESS AND TALLNESS TRAITS WERE INHERITED IN THE F1 PLANT, BUT ONLY THE TALLNESS WAS EXPRESSED. 

IN THIS EXPLANATION, BOTH Tt AND TT ARE TALL PLANTS, WHILE ONLY Tt IS A SHORT PLANT TRAIT. IN OTHER WORDS A SINGLE COPY OF 'T'  IS ENOUGH TO PRODUCE THE PLANT TALL, WHILE COPIES NEED TO BE 't' FOR THE PLANT TO BE SHORT. TRAITS LIKE 'T' ARE KNOWN AS DOMINANT TRAITS, WHILE THOSE THAT BEHAVE LIKE 't' ARE KNOWN AS RECESSIVE TRAITS.