Genetics & Plant Breeding

Fundamental Of GPB

Hello! Welcome To Agriculture At A Glance

Here we study about everything about agriculture. Like some main subjects, some important key points. and previous year competitive exam’s MCQ question paper.

If agriculture goes wrong, nothing else will have a chance to go right.

- M. S. Swaminathan

Introduction to Genetics and Plant Breeding

Genetics is a branch of biology which deals with the study of genes, genetic variation and heredity. Plant breeding is an art, science and technology of developing superior plants of economic utility for the mankind.

Definition of Genetics

Genetics is a branch of biology which deals with the study of genes, genetic variation and heredity.

Genetics is derived from the Greek word genesis that means to become or to grow. The Term Genetics was coined by Bateson in 1905.

The Father of Genetics

Gregor Johann Mendel is the father of modern genetics.

Plant Breeding

Plant breeding is an art, science and technology of developing superior plants of economic utility for the mankind.

1. Steps Of Plant Breeding

2. Why We Breed A Plant


The study of chromosome, which are long strands of DNA and protein that contain most of the genetics information in a cell


DNA stands for Deoxyribonucleic acid and it is Hereditary material. Most DNA is located in the cell nucleus (where it is called nuclear DNA), but a small amount of DNA can also be found in the mitochondria (where it is called mitochondrial DNA).

In 1953, James Watson and Francis Crick proposed the double helix structure of DNA in their paper “Genetical Implications of the Structure of Deoxyribonucleic Acid”

DNA contains the code for building and maintaining an organism. The code is spelled out in the order, or sequence, of four chemical bases—adenine (A), guanine (G), thymine (T) and cytosine (C). DNA bases pair with each other—adenine (A) with thymine (T), guanine (G) with cytosine (C) —to form units called base pairs. Each base is attached to a sugar molecule and a phosphate molecule. Together, base, sugar, and phosphate are called a nucleotide. Nucleotides are arranged in two long strands that form a spiral called a double helix.


It is the functional unit of DNA. Genes are made up of sequences of DNA and are arranged, one after another, at specific locations on chromosomes in the nucleus of cells. (# pic of gene)

The term ‘Gene’ was coined by Wilhelm Johannsen in 1909


A genome is the complete set of genetic information in an organism. It provides all of the information required by an organism to function.


Alternate form of the gene is known as allele. An allele is one of two or more versions of DNA sequence (a single base or a segment of bases) at a given genomic location. An individual inherits two alleles, one from each parent, for any given genomic location where such variation exists. If the two alleles are the same, the individual is homozygous for that allele.

The term ‘Allele’ was coined by W. bateson as ‘Allelomorph’


Chromosomes are thread-like structures located inside the nucleus of animal and plant cells. Each chromosome is made of protein and a single molecule of deoxyribonucleic acid (DNA).


Having two same alleles of a gene is called Homozygous.


Having two different alleles of a gene is called Heterozygous.


Similar gene makeup of the population. Homogeneous comes from the Greek words hom-, meaning “same,” and genos- meaning “kind.” The similar word homogenous is a synonym of the same origin.
EX:- Pure line


Different gene makeup of the population. Heterogeneous comes from the Greek words Hetero-, meaning “different,” and genos, meaning “kind.” The similar word Heterogeneous is a synonym of the different origin.
EX:- MAS Selection

Pure Line

A pure line means those breeds of organisms that have been generated through repeated self fertilization and have become homozygous for a particular trait.

MAS selection

Marker-assisted selection or marker aided selection (MAS) is an indirect selection process where the desired trait is selected based on a marker(morphological, biochemical or DNA/RNA variation) linked to a trait of interest (e.g. productivity, disease resistance, tolerance, and quality), rather than on the trait itself.


The allele which will be expressed in heterozygous form is dominant.
Ex:- TT × tt (Here ‘TT’ is dominant)


The allele which will not be expressed in heterozygous form but expressed in homozygous form is recessive.
Ex:- TT × tt (Here ‘tt’ is recessive)

Homologous chromosome

The chromosomes having the same chromatide length bearing the same genes are known as homologous chromosomes.

Gene Locus

A fixed position of a gene on a chromosome is known as gene locus.


Variations are the differences present between the individuals of the same species or different species.


The transmission of traits from parents to their off-spring(Child) is known as heredity. The mode of transmission is known as inheritance.


The progeny of crosses between different varieties of a plant species usually exhibit greater biomass and fertility than either parent. This phenomenon is called heterosis or hybrid vigor.


A trait is a particular characteristic, quality, or tendency that someone or something has.
Ex:- eye colour, height, ears, hair colour etc..


An external or physical characteristic that appears in an organism is called phenotypes.
Ex:- eye colour, height, ears, hair colour etc..


It refers to the genetic makeup of an organism.
Ex:- Homozygous Dominant (TT), Heterozygous (Tt), Homozygous Recessive (tt)


Any changes in the DNA sequence of a cell is called mutation. Mutations may be caused by exposure to DNA-damaging agents in the environment. Mutations can be harmful, beneficial, or have no effect.


Anything that causes a mutation (a change in the DNA of a cell) is called mutagen.