What is Genetics and their Bases?

Genetics is the study of Heredity and Variation in the living organism according to time. Genetics term was given by W.Batson.
Heredity:- Study of transmission of genetic characters from parent to offspring.

Variation:- Differences that are seen among the members of the same species.

Inheritance:-It is the process by which genetic characters are transferred from parent to offspring.

IMPORTANCE:-

  • Genetics helps to determine the molecular structure and function of genes.
  •  It helps to determine the pattern of gene distribution in an organism.
  • Genetics is the variation and change in population.

HISTORY OF RESEARCH IN GENETICS 

It was during the mid-nineteenth century that headway was made in the understanding of inheritance. Gregor Mendel conducted hybridization experiments on garden peas for seven years (1856-1863) and proposed the laws of inheritance in living organisms
  • Gregor Johann Mendel:- Father of Genetics
  • W. Bateson:- Father of Modern Genetics.
  •  He proposed various terms like Genetics, Allele, Homozygous, Heterozygous.
  • T. H. Morgan:- Father of Experimental genetics 
  • He performed experiments on Drosophila.
  • He proposed various concepts like Linkage, Sex linkage, Crossing over, Crisscross inheritance.
  • He suggested that genes are linearly arranged on chromosomes.
  • A. Garrod:- Father of human genetics and Biochemical genetics.
  • Garrod discovered the first human metabolic genetic disorder:- Alkaptonuria (Black urine disease)

SOME GENETICAL TERMS 

  • Character:- Any feature of an organism. e.g.:- Stem height, Flower color
  • Trait:- Variable form of a character. e.g. :- Tall/Dwarf.
  • Gene (term by Johannsen):- Mendel used the term “ Element ” or “ Factor ”. A segment of DNA that is responsible for the appearance of characters. 
  • The segment of DNA generally synthesizes RNA which may or may not synthesize protein. Gene:- Unit of inheritance Chemically gene is:- DNA
  • Alleles:- Alternate form of a gene is called an allele. • Allele arises due to mutation. • Allele is present at the same locus (location) on homologous chromosomes.
  • Unmodified allele/wild allele/original type:- Allele which is present in nature from starting. The generally unmodified allele is the dominant allele.
  • Modified allele:- It is formed by a mutation in the original allele. A generally modified allele is a recessive allele.



  • Homozygous/ Pure/ True breeding:- Presence of two similar alleles of a gene in a diploid organism.Ex- TT, tt

  • Heterozygous/ Impure:- Presence of two dissimilar alleles of a gene in a diploid organism.  Ex- Tt

  • Hemizygous:-In diploid organisms, presence of single allele of a gene. Ex- genes present on X and Y chromosomes of human males.
  • Dominant Allele:- Allele that can express both in homozygous and heterozygous conditions. e.g. :- T allele
  • Recessive Allele:- Allele that can express only in homozygous conditions. e.g.:- t allele

  • Phenotype:- The external appearance of an organism for a particular character. Ex- Tall/ Dwarf.
  • Genotype:- The genetic constitution or genetic make-up of an organism for a particular character. Ex- TT/ Tt/ tt

Phenocopy:- When two different genotypes place under different environmental conditions and develop similar phenotypes, they are called phenocopy of each other.


Genome:- Total genetic material present in a haploid cell of an organism.



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