The branch of biological science of inheritance which deals with the study of heredity and variation is called genetics. Gregor Johann Mendel is considered as father of genetics because the first scientific study of genetics was carried by him and introduced the concept of genes as the basic unit of heredity.

Heredity is the phenomenon by which Living organisms transmit parental characteristics to their off springs.
Heredity characteristicsare the characteristicsof the parents which are transmitted to their off springs.
Any too examples are:
- Type of hair in Human beings.
- Color of the eyes.

The tiny units of heredity located in the chromosomes is called genes.
The concept of 'gene' was introduced by sulten and the term 'gene' was introduced by Johannsom. It is located in chrosomes and arranged in linearfashion. It determine the physical, anatomical andphysiologicalcharacteristicsof organism. These characteristics are transmitted from one generation to other.

Allelomorph is one of a gene or pair of matchinggenes. It contains a pair of identical alleles.

When the both alleles of a particular gene areidentical, it is called homozygous.

When two alleles of a particular gene arenot identical, it is calledheterozygous.

The organism produced after cross fertilization between two genetically different organisms iscalled hybrids.
Hybrids are produced by crossing between organismshaving two contrasting characteristics. This process is called hybridization.

Mendel selected pea plant for his study because of following reasons:
- Pea plant can be cultivated easily and have a short life cycle.
- Breeding controlled easily.
- Pea plant produce large number of off springs after fertilization.
- The flower of pea plants are adequate in size and easy to handle.
- Pea plant are found in various species.

a.Genotype and Phenotype.

b.Dominant characteristics and Recessivecharacteristics.

Mendel's law of dominance states that, "In a crossingbetween pure organism for constrasting characteristicsof a pair, only onecharacteristicsof a pairappears in thefirst filialgeneration.
Let us consider a pure tall pea plants (TT) anda pure dwarf pea plant (tt). When a pure tall peaplant is cross pollinatedwith the puredwarfone, allthe off springs will be tall in firstfilial generation. Here, tallness appears by suppressing the dwarfness.In this cross, tall is the dominant characteristicsasit...

Law of segregation states that, "The hybrid obtained in F₁generation contains two contrasting characteristics of dominant and ressive in nature. Those characteristics remain together for long time in hybrids but don't mix with each other and separates at the time of gametes gets only a pure characteristics."
The monohybrid cross between a pure red floweredpea plant and pure white floweredpea plant up to the2nd filial generation. In F₁ generation all pea plantsproduced hybrid red (Rr) with...

Dihybrid cross is the crossin which to pairs of constracting characteristics are taken into consideration.
For example: Cross between red-flowered tall pea plant and white flowered dwarf pea plant.

Yes, Mendel's law applies the human beings also.
Any two difficulties that Mendel would have faced if he had carried his experiments on human beings instead of pea plants are:
- Human beings have long term life cycle. It is impossible to observe many generations.
- It is impossible to cross between siblings.
- Human being have many contrasting characters which makes difficult to study them.
- It is easier to handle pea plant than human as fertilization and reproduction process is easier and...

The difference between mutation and variation are:

a. Which filial generation does this result belongs to?
-This result belongs to 2nd filial generation.
b. What is the percentage of pea plant having hybrid characteristics?
-50 percentage of pea plant have hybrid characteristics.
c. Which pair of genes indicate pure tall plant?
-(IT) indicates pure tall pea plant.

Here,

Here,
Bb is a black mice because B is dominant character and bb is a pure white mice.
So,
Total black mice (Bb) = 2
And total white mice (bb) = 2
So, phenotype ratio = 2 : 2
= 1 : 1

The significance of Mendelism are
- Diseases resistantand high yielding varieties of plantsand animals can be produced by application of Mendelism.
-Hybrids with desired characteristics can be produced.
-The genotypes and phenotypes likely to be produced insuccessive generations can be predicted before the cross is made.
-Dominant and recessive characteristics oforganismcan be known.

The structural differences that provide individualityto each member of a species is called variation.
The factors that bring out geneticvariation are:
- Structural and functional differences of a gene.
- Environmental factors like food, light, temperature, etc.