To get the best deal on Tutoring, call 1-855-666-7440 (Toll Free)


Genetics is a science, which deals with the study and understanding of heredity, evolution, development, ecology, molecular biology and forensic science. A German scientist by name Gregor Johann Mendel was a first founder of Genetics, hence he is also known as the father of genetics. He first demonstrated the inheritance of traits in pea plants and later it was referred to as a Mendelian inheritance.

The main concept behind studying genetics are:
  • It explains how the traits are passed from parents to their off springs.
  • It also explains about the gene and the number of chromosomes present in an individual with their importance.


Variation of Species

Back to Top
The term variation can be defined as the range of differences between individual organisms. This variation occurs within the species. For example differences between individual human beings. This variation is of two types:
Variation of Species
Continuous Variation: In this variation all types of features have a normal distribution.

For example: Height of individual human beings, width of a leaf, weight of a cat, etc.

This image shows an example of  continuous variation -  height of individual human beings.
 Height of Individual Human Beings
Discontinuous Variation: In this case, there are only a few features, which fall under the category of discontinuous variation.

For example: Different colour of flower in a single plant species, different types of blood groups in individual human beings,  different types of ear lobe, etc.

This image shows an example of  discontinuous variation - different colour of flower in a single plant species

Different Colour of Flower


Back to Top
The term heredity can be defined as the process of transferring the characters or the traits from the parents to their offspring. In this  process of transformation, the characters gets transferred through the genes present in the DNA. These DNA's are present in the chromosomes, which are present in the nucleus of the cell. The transferring  of the characters, includes the contribution of equal amount of genetic material from both the parents (mother and father) to their offspring.

Gene Expression

Back to Top
Before moving into gene expression, let us know something about a gene. 

What is a Gene?

A gene is a segment of the DNA, which contains all sorts of information that are required for coding some important functions. Hence a gene is called as a unit of information. Every cell in an organism have a similar set of  genes. A gene  is transferred  from the  parents to their offsprings. The term gene was coined by the scientist named Johann sen in the year 1909.

Gene expression is the activation of a gene, which results in a protein. Gene expression is the process by which the genetic information is used  in the synthesis of a gene. This process  is generally used  in all eukaryote, prokaryotes and in viruses  for  generating  the macromolecular machinery of life.

Genetic Code

Back to Top
A code that contains all types of genetic information, which are  present in the nucleotide sequences of  DNA or RNA and are later translated into proteins by the living cells. These codes can be expressed  either as RNA codons or DNA  codons. These code instructs a gene to guide the cell to make a specific protein. A,T,G,C is the alphabetical letter of the DNA code. These letters stand for adenine, thymine, guanine and cytosine, which completely make up the nucleotide bases of DNA. Each and every code combines with these four chemicals for the synthesis of proteins.

DNA Structure

Back to Top
DNA is called the blueprint of life as it contains  all  types of  instructions for making proteins within the cell. It is very long polymer and the basic shape of the DNA is  just  like a twisted ladder. Hence it is also called as a double helices DNA. The backbone of the DNA molecule is alternating phosphates, deoxy Ribose sugar and  nitrogenous bases. The information in DNA is stored as a code made up of four chemical bases: adenine (A), guanine (G), cytosine (C), and thymine (T).

Structure of DNA

Structure of DNA

Genetic Inheritance

Back to Top
It can be defined as the  transformation of traits from the  parents to their offspring. Everyone has two copies of every gene among which one inherited from the mother cell  and another one is inherited from the father cell . 

Causes of Variation and Evolution.

There are mainly two factors, which are responsible for variation  and evolution of species. They are:
Genetic variation: In this case,difference in variation is mainly due to the presence of DNA inside the cells of an organism. The features of each species will be different in their colour, size and shape because they come from the parent with different alleles, which codes for different characteristics.

This image shows an example of genetic variation in the shape of tomatoes.

Shape of Tomatoes

Environmental variation: In this case the difference in variation is mainly due to the external environmental conditions like water, light, temperature, wind, nutrients, pH of a soil, etc. For example:   All features of plant species will be genetically identical but the differences are mainly seen in the colour of the flower, which is due to the effects of the environment.

This image shows an example of  environmental  variation in  plant species, which are  genetically identical but the differences are mainly seen in the colour of the flowers.

Dahlia Flower
More topics in Genetics
Stem Cells Barr Bodies
Mendelian Genetics Non-Mendelian Genetics
Patterns of Inheritance Chromosomal Mutations
Chromosomes Sex Determination
Sex Linkage Bacterial Genetics
Central Dogma DNA Replication
DNA Transcription DNA Translation
Gene Regulation Blood Type Genetics
Molecular Genetics DNA
NCERT Solutions
NCERT Solutions NCERT Solutions CLASS 6 NCERT Solutions CLASS 7 NCERT Solutions CLASS 8 NCERT Solutions CLASS 9 NCERT Solutions CLASS 10 NCERT Solutions CLASS 11 NCERT Solutions CLASS 12
*AP and SAT are registered trademarks of the College Board.