03 Inheritance and Variation - part 01 - Chromosomes and Mechanism of inheritance part 1 st

03 Inheritance and Variation - part 01 - Chromosomes and Mechanism of inheritance


Chromosomes and Mechanism of inheritance :

  • The transmission of genetic information from generation to generation is known as heredity or inheritance. 
  • The mechanism of inheritance was successfuly investigated before chromosomes had been observed or genes were known. 
  • Gregor Mendel, son of the peasant farmer, was born in Moravia in 1822. 
  • Gregor Mendel first gave the accurate explanation for the mechanism of inheritanceby using hybridization technique. 
  • Inheritance of the seven traits in garden pea(Refer the diagram below) plant were studied individually one at a time or in combination of two or three character at a time. 
  • He processed the data mathematically and statistically. 
  • Mendel postulated the principles of heredity which then became the fundamental laws of heredity, as proposed by Correns (1900). 
  • He visualized that the traits as such are not inherited physically but by `something' present inside the gametic cell. 
  • To this `something', he coined term `factors'that are responsible for expression of a particular trait/ character. 
  • He proposed that factors are particulate in nature. 
  • The Mendelian factors are now termed as `genes'. 
  • These factors occur in pairs in the parents and segregate from each other during gamete formation without blending/ mixing.


Reasons for Mendel's Success : 

  • His experiments were carefully planned and involved large sample. 
  • He carefully recorded the number of plants of each type and expressed his results as ratios.
  • In the pea plant, contrasting characters can be easily recognized. 
  • The seven different charaters in pea plant were controlled by a single factor each. 
  • The factors are located on separate chromosomes and these factors are transmitted from generation to generation. 
  • He introduced the concepts of dominance and recessiveness. 

No comments:

Post a comment

Subscribe to: Posts (Atom)

Comments

Post a Comment

Popular posts from this blog

6. Biomolecules - part 01 - Carbohydrates

Image
  6. Biomolecules - part 01 - Carbohydrates Introduction : Our planet is having a wide diversity of living organisms that are classified as - unicellular  (consisting of a single cell; including bacteria and yeast) or  multicellular  having many cells (e.g. plants and animals).  living organisms have cell as the basic structural and functional unit.  The cells have protoplasm containing numerous chemical molecules, the biomolecules. Biochemistry  : Biochemistry is  biological chemistry  that provides us the idea of the chemistry of living organisms and molecular basis for changes taking place in plants, animals and microbial cells.  It develops the foundation or understanding  all biological processes  and communication within and between cells as well as chemical basis of inheritance and diseases in animals and plants. Chemical analysis of all living organisms indicates presence of the most common elements like  carbon, h...
Read more

6. Biomolecules - part 02 - Lipids

Image
  6. Biomolecules - part 02 - Lipids B. Lipids : These are group of substances with greasy consistency with  long hydrocarbon chain containing carbon, hydrogen and oxygen. In lipids, hydrogen to oxygen ratio is  greater than 2:1  (in carbohydrates it is always 2:1). Lipid is a broader term used for fatty acids and their derivatives.  They are soluble in organic solvents (non-polar solvents).  Fatty acids are organic acids which are composed of hydrocarbon chain  ending in carboxyl group (-COOH).  They can be  saturated fatty acids  with no double bonds between the carbon atoms of the hydrocarbon chain.  Palmitic and stearic acids  found in all animal and plant fats are examples of saturated fatty acids. Unsaturated Fatty Acids  are with one or more double bonds between the carbon atoms of the hydrocarbon chain.  Oleic acid  found in nearly all fats and  linoleic acid  found in many seed oils are example...
Read more

6. Biomolecules - part 05 - Enzymes

Image
  6. Biomolecules - part 05 - Enzymes Enzymes : Thousands of different chemical reactions take place automatically at a given time in a tiny living cell. The reactions take place at the body temperature.  If these enzymes were not present in the cell, either the reactions would not occur or if they occur they would occur at a  very very slow rate . Know the scientists : German chemist  Edward Buchner  discovered enzymes by accident.  Buchner discovered that living cells were not necessary but that  yeast  extract could bring about fermentation.  He then coined the term Enzyme (Gk. En = in, zyma = yeast i.e. in yeast). This term is now commonly used for all biocatalysts. Each enzyme catalyzes a small number of reactions, specifically perhaps only one. Substrate :  The substance upon which an enzyme acts is termed as the substrate.  Endo-enzymes :  The enzymes which act within the cell in which they are synthesizedare known as en...
Read more