Samacheer Class 10 Science - Breeding and Biotechnology

Importance of Biofertilizers : The term biofertilizer denotes all nutrient inputs of biological origin for plant growth Eg: Artificial inoculation of rice with cyanobacteria to increase soil fertility.
Significance :
(i) They are ecofriendly.
(ii) They do not cause pollution like artificial fertilizers.
(iii) Help to Safeguard natural resources.
(iv) They are cheaper and economical.

(i) Sometimes cells, tissues and organs in the body may be permanently damaged or lost due to genetic condition or disease or injury.
(ii) In such situations stem cells are used for the treatment of diseases which is called stem-cell therapy.
(iii) In treating neurodegenerative disorders like Parkinsv./s disease and Alzheimer’s disease neuronal stem cells can be used to replace the damaged or lost neurons.

Objectives of Animal Breeding :
Heterosis or Hybrid vigour: The superiority of the hybrid obtained by cross breeding is called as heterosis or hybrid vigour.
Effects of hybrid vigour in animal breeding :
(i) Increased production of milk by cattle.
(ii) Increased production of egg by poultry.
(iii) High quality of meat is produced.
(iv) Increased growth rate in domesticated animals.
Examples :
Cross breed of fowls
White Leghorn X Plymouth Rock
↓
Hybrid fowl - yield more eggs
Cross breed of cows
Developed by mating the bulls of exotic breeds and cows of indigenous breeds.
Brown Swiss X Sahiwal
↓
Karan Swiss - yield 2-3 times more milk than indigenous cows.

Mutation is defined as the sudden heritable change in the nucleotide sequence of DNA in an organism. It is a process by which genetic variations are created which in turn brings about changes in the organism. The organism which undergoes mutation is called a mutant.
Two types of mutagens : The factors which induce mutations are known as mutagens or mutagenic agents.
(i) Physical mutagens: Radiations like X-rays, \alpha , \beta and \gamma -rays, UV rays, temperature etc. which induce mutations are called physical mutagens.
(ii) Chemical mutagens : Chemical substances that induce mutations are called chemical mutagens. Eg: Mustard gas and nitrous acid. The utilisation of induced mutation in crop improvement is called mutation breeding.
Achievements of mutation breeding :
Some achievements of mutation breeding are
(i) Sharbati Sonora wheat produced from Sonora-64 by using gamma rays.
(ii) Atomita 2 rice with saline tolerance and pest resistance.
(iii) Groundnuts with thick shells.

(i) Hidden hunger is a chronic lack of vitamins and minerals that often has no visible warning signs. People who suffer from it may not even be aware of it.
(ii) This can lead to severe consequences. Hidden hunger may lead to mental impairment, poor health and productivity or even death.
Biofortification :
Biofortification is the scientific process of developing crop plants enriched with high levels of desirable nutrients like vitamins, proteins and minerals. Some examples of crop varieties developed as a result of biofortification are given below:
(i) Protina, Shakti and Rathna are lysine rich maize hybrids (developed in India).
(ii) Atlas 66, a protein rich wheat variety.
(iii) Iron rich fortified rice variety.
(iv) Vitamin A enriched carrots, pumpkin and spinach.

Gene Cloning :
(i) A clone is a genetically exact copy of an organism.
(ii) In gene cloning, a gene or a piece of DNA fragment is inserted into a bacterial cell where DNA will be multiplied (copied) as the cell divides.
Basic steps involved in gene cloning :
(i) Isolation of desired DNA fragment by using restriction enzymes.
(ii) Insertion of the DNA fragment into a suitable vector (Plasmid) to make rDNA.
(iii) Transfer of rDNA into bacterial host cell (Transformation).
(iv) Selection and multiplication of recombinant host cell to get a clone.
(v) Expression of cloned gene in host cell.
Using this strategy several enzymes, hormones and vaccines can be produced.

Using genetic engineering techniques medicinally important valuable proteins or polypeptides that form the potential pharmaceutical products for treatment of various diseases have been developed on a commercial scale.
Pharmaceutical products developed by rDNA technique :
(i) Insulin used in the treatment of diabetes.
(ii) Human growth hormone used for treating children with growth deficiencies.
(iii) Blood clotting factors are developed to treat haemophilia.
(iv) Tissue plasminogen activator is used to dissolve blood clots and prevent heart attack.
(v) Development of vaccines against various diseases like Hepatitis B and rabies.
IX Higher Order Thinking Skills (HOTS)

Green revolution is the process of increasing food production through high yielding crop varieties and modern agricultural techniques in under developed and developing nations. This has increased production and helped India tide over food crisis. But this requires high yielding varieties of crops got by artificial methods like breeding, use of fertilizers and pesticides.
Some disadvantages have been listed below :
(i) This promotes monoculture of certain desired plant varieties.
(ii) Use of fertilizers I pesticides in excess alters the chemical composition of the soil.
(iii) All farmers cannot afford the cost.
(iv) Environmentalists felt that because of green revolution the soil was affected and certain traditional crops varieties have been neglected.
Organic Farming :
(i) In contrast organic farming avoids utilization of synthetic fertilizers, chemical pesticides and makes use of green manures, compost and biological pest control which do not harm the environment.
(ii) Further growing different plant species will lead to efficient use of nutrients and cause fewer outbreaks of disease.
(iii) Organic farming techniques like Inter cropping, use of companion plants will also increase biodiversity. Thus organic farming is stable, sustainable and beneficial for the future generations.