Notes on History of Genetics and Cytogenetics

1. History of Genetics and Cytogenetics

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Source: Principles of Genetics and Plant Breeding by BD Singh 

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History of Genetics and Cytogenetics:

• Genetics is the science of inheritance and variation.
• Genes are the functional units governing individual characteristics.
• Characters include morphological, anatomical, physiological, and behavioral features.
• Examples of human characters are eye color, hair color, blood groups, etc.
• Variation in characters indicates variation in the genes governing them.
• Cytogenetics studies chromosomes and their effects on organism development.
• Genes are universally accepted to be located in chromosomes.
• Cytogenetics originated by combining cytology and genetics.
• Cytology is the study of cell structures and functions.
• Genetics and cytogenetics are distinct grossly but not at the molecular level.

Spontaneous Generation:

• Organisms originate from pre-existing organisms of the same kind.
• Living organisms do not arise from nonliving matter.
• Spontaneous generation was believed by some biologists but refuted.
• Redi and Spallanzani presented evidence against spontaneous generation.
• Pasteur and Tyndall conclusively proved microbes do not originate spontaneously from organic matter.

Reproduction in Plants and Animals:

• Babylonians and Assyrians knew about pollination in palm trees.
• Eggs of birds were known, but mammalian eggs discovered later.
• De Graaf identified mammalian ovarian vesicles as eggs.
• Leeuwenhoek studied sperms but didn't speculate on fusion.
• Spallanzani proved sperm's essential role in progeny development.
• O. Hertwig provided conclusive proof of sperm-egg nucleus fusion.
• Thomas Fairchild produced the first artificial plant hybrids in 1717.
• Linnaeus, Koelreuter, and Gaertner produced artificial plant hybrids.
• Amici described pollen tube entry into the ovary.
• Strausberger described fertilization in angiosperms in 1884.

Preformation:

• Heredity debate about the contribution of male and female parents.
• Aristotle believed progeny form came from semen, substance from females.
• Animalculists and ovists developed these concepts further.
• Some claimed to see "homunculus" in human sperms.
• Preformationists believed miniature human beings were in gametes.
• Preformationists thought progeny developed from preexisting beings.
• Improved microscopes challenged the idea of preformation.
• Epigenesis replaced preformation as the accepted view.

Epigenesis:

• Organs and tissues of adults develop from uniform embryonic tissues.
• Differentiation from homogeneous embryonic tissues leads to organs.
• Wolff proposed epigenesis but believed adult tissues originated de novo.
• Von Baer suggested that adult tissues developed from embryonic tissues.
• Von Baer's concept is the universally accepted view of organ development.

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History and Speciality of Triticale -for All Agriculture Exams IBPS ADO, RAEO, JRF, SRF & CUET Target Exam

This exam facts are from famous book: Handbook of Agriculture published by I C A R

History of Triticale

• Triticale is a Man madecereal.
• Triticale is a hybrid of wheat (Triticum) and rye (Secale) first bred in laboratories during the late 19th century in Scotland and Germany.(This is asked in Rajasthan Agriculture Officer Exam 2020)
• Triticale is a hybrid or intergeneric cross that is made by the crossing of wheat and rye.(This is asked in ICAR S R F 2021)
• Triticale is first wheat x rye that occurred in Scotland during 1875.(This is asked in IBPS Agriculture Field Officer Exam 2019)
• The name Triticatefirst appeared in Germany in 1935.(This is asked in B H U PRE P G 2020)
• Triticale, hexaploid cultivars are most commonly used. 
• Hexaploids of wheat and rye are called primary hexaploids.For free such exam facts and notes, visit www. agrimly.in 
• Triticale is either spring or winter cultivated. 
• Majority of triticale cultivars are awned.
• Initial cultivars are, low yielder, tall and weak straw, shrunken/shriveled kernels, high susceptibility to ergot. But high protein, high levels of amino acids and good for animal nutrition.
• Commercially available triticale is almost always a second generation hybrid, i.e., a cross between two kinds of primary (first cross) triticales.(This is asked in ICAR J R F 2021)
• As a rule, triticale combines the yield potential and grain quality of wheat with the disease and environmental tolerance including soil conditions of rye.For Online Classes, Tests, Notes Visit www. agricoachingonline.com
• But today’s cultivable triticale has better yielding ability than wheat, more tiller producing habit, resistance to lodging, resistance to ergot, plump kernels, and protein is similar to bread wheat, suitable for spring and winter seasons.

Speciality of Triticale

• Triticale can utilize water and nutrients more efficiently than winter wheat.
• Seeding, seed rate, season, etc. are similar to wheat.
• Nutrient and water requirements are similar to wheat and they are responding well when grown for grain.
• For forage, the seed rate may be enhanced to 80-100 kg in rainfed and drylands.
• For irrigated crops about 110 kg of seed rate is adopted.(This is asked in IBPS Agriculture Field Officer Exam 2015)
• Since the complete package of practices for triticale are not developed, cultural practices of wheat are utilized for cultivating triticale

Speciality Baby Corn - for All Agriculture Exams IBPS AFO, ADO, RAEO, JRF, SRF, CUET EXAM

This exam facts are from famous book: Handbook of Agriculture published by I C A R

• Baby corn also known as young corn, cornlets or baby sweetcorn is a cereal grain taken from corn (maize) harvested early.
• Baby com is a young finger like unfertilized cobs with 1 -3 cm emerged silk preferably harvested within 1-3 days of silk emergence, depending upon the growing season.(This is asked in IBPS Agriculture Field Officer Exam 2014)
• Baby corn is nutritive and its nutritional quality is at par or even superior to some of the seasonal vegetables.For free such exam facts and notes, visit www. agrimly.in 
• Besides proteins, vitamins and iron, baby corn is one of the richest sources of phosphorus.(This is asked in ICAR J R F 2021)
• Baby corn is a good source of fibrous protein and easy to digest.(This is asked in ICAR S R F 2019)
• For Online Classes, Tests, Notes Visit www. agricoachingonline.com
• Baby corn is almost free from residual effects of pesticides. 
• As baby corn can be cultivated round the year, three to four crops of baby corn can be taken in a year.(This is asked in M P Agriculture Development Officer Exam 2018)

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GENETICS & PLANT BREEDING (SYLLABUS FOR ICAR’S JRF/SRF(PGS) )

SYLLABUS FOR THE ALL INDIA COMPETITIVE EXAMINATION FOR ADMISSION TO DOCTORAL DEGREE PROGRAMMES AND THE AWARD OF

JRF/SRF (PGS)

01. GENETICS & PLANT BREEDING

Unit 1: General Genetics and Plant Breeding

Mendelian inheritance. Cell structure and division, Linkage, its detection and estimation. Epistasis.

Gene concept, allelism and fine structure of gene. Extra chromosomal inheritance. DNA - structure,

function, replication and repair. Genetic code. Gene-enzyme relationship. Replication, Transcription

and Translation. Gene regulation in prokaryotes and eukaryotes. Nuclear and cytoplasmic genome

organization. Spontaneous and induced mutations and their molecular mechanisms. Crop

domestication, evolution of crops and centres of diversity. Emergence of scientific plant breeding.

Objectives and accomplishments in plant breeding and the role of National and International institutes

. Gametogenesis and fertilization. Modes of sexual and asexual reproduction and its relation to plant

breeding methodology. Apomixes, incompatibility and male sterility systems and their use in plant

breeding. Epigenetics.

Unit 2: Economics Botany and Plant Breeding Methods

Origin, distribution, classification, description and botany of cereals (wheat, rice, maize, sorghum,

pearl millet, small millets); pulses (pigeonpea, chickpea, black gram, green gram, cowpea, soybean,

pea, lentil, horse gram, lab-lab, rice bean, lathyrus, lima bean; oilseeds (groundnut, sesamum, castor,

rapeseed mustard, sunflower, safflower, niger, linseed); fibre and sugar crops, fodder and green

manures; Breeding methods for self-pollinated, cross-pollinated and asexually propagated crops.

Combination, recombination and transgressive breeding. Single seed descent. Populations, their

improvement methods and maintenance, Hybrid breeding and genetic basis of heterosis. Ideotype

breeding. Mutation breeding, Concept of tree breeding. Speed breeding methods, Pre-breeding,

Reverse Breeding.

Unit 3: Genome Organization and Cytogenetics of Crop Plants

Chromosome number, structure, function and replication. Sex determination & sex linkage.

Recombination and crossing over. Molecular and cytological mechanism of crossing over.

Karyotype analysis.Chromosomal theory of inheritance. Cell cycle and its regulation. Banding

techniques. In situ hybridization. GISH and FISH Special types of chromosomes. Chromosomal

interchanges, inversions, duplications and deletions. Polyploids, haploids, aneuploids, their utility and

their meiotic behaviour. Wide hybridization and chromosomal manipulations for alien gene transfer.

Pre-and post- fertilization barriers in wide hybridization. Genome organization and Cytogenetics of

important crop species- wheat, maize, rice, sorghum, Brassica, groundnut, cotton, Vigna, potato and

sugarcane. Cytogenetic techniques for gene location and gene transfer, Construction and use of

molecular marker based chromosome maps.

Unit 4: Quantitative and Biometrical Genetics

Quantitative characters. Multiple factors inheritance. Genetic control of polygenic characters. Genetic

advance and types of selection their effects on population mean and variance. Metric characters under

natural selection. Repeatability and asymmetry of response. Breeding value. Dominance and

interaction deviations. Hardy Weinberg law and changes in gene frequency due to migration, mutation

and selection. Linkage disequilibrium. Genetic load. Polymorphism. Breeding value, heritability.

Response to selection, correlated response. Estimates of variance components and covariance

among relatives. Mating designs with random and inbred parents. Estimation of gene effects and

combining ability. Effects of linkage and epistasis on estimation of genetic parameters. Maternal effects.

Genotype-environment interactions, stability of performance and stability analysis. Heterosis and its

basis (Genetic, biochemical and physiological). Mating system and mating design-diallel, line X tester,

NC-I NC-II and NC-III designs, approaches to estimate and exploit components of self and cross

pollinated crops. . GGE biplot analysis, Principal component analysis, AMMI and GGI analysis.

Unit 5: Genetic Engineering and Biotechnological Tools in Plant Breeding

Somatic hybridization, micropropagation, somaclonal variation, in vitro mutagenesis. Anther culture.

Cryopreservation. Genetic and molecular markers, generation of molecular markers and their

application in genetic analyses and breeding. Molecular markers in genetic diversity analysis and

breeding for complex characters. Gene tagging, QTL mapping, MAS, MARS and MABB. Vectors.

DNA libraries, DNA fingerprinting, DNA sequencing. Nucleic acid hybridization and immunochemical

detection. Chromosome walking, Recombinant DNA technology, Gene cloning strategies. Gene

transfer methods. Artificial synthesis of gene. Genetic transformation, transgenics and cisgenics.

Antisense RNA, RNAi and micro RNA techniques in crop improvement. Genome editing using

CRISPER/cas, Genomic selection, RNA Seq analysis,

Unit 6: Plant Breeding for Stress Resistance and Nutritional Quality

Genetic and molecular basis and breeding for resistance to diseases and insect-pests. Breeding for

vertical and horizontal resistance to diseases. Genetic and physiological basis of abiotic stress

tolerance. Breeding for resistance to heat, frost, flood, drought and soil stresses. Important quality

parameters in various crops, their genetic basis and breeding for these traits. Role of molecular

markers in stress resistance breeding using biotechnological tools (MAS, MARS and MABB and

transgenics). Biofortification.

Unit 7: Plant Genetic Resources and their Regulatory System; Varietal Release and Seed Production

Plant exploration, germplasm introduction, exchange, conservation, evaluation and utilization of plant

genetic resources. Types of genetic resources. Centres of diversity of cultivated plants. Genetic erosion

and genetic vulnerability. Convention on Biological Diversity and International Treaty on Plant Genetic

Resources for Food and Agriculture. Intellectual Property Rights and its different forms for protection

of plant genetic resources. Biodiversity Act. Protection of Plant Varieties and Farmers' Rights Act and

its features. System of variety release and notification. Types of seeds and seed chain. Maintenance

breeding- nucleus and breeder seed production. Seed production and certification.

Unit 8: Statistical Methods and Field Plot Techniques

Frequency distribution. Measures of central tendency, probability theory and its applications in genetics.

Probability distribution and tests of significance. Correlation, linear, partial and multiple regression.

Genetic divergence. Multivariate analysis. Designs of experiments - basic principles, completely

randomized design, randomized block design and split plot design. Complete and incomplete block

designs. Augmented design, Grid and honeycomb design. Hill plots, unreplicated evaluation. Data

collection and interpretation.