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Apart from monohybrid, dihybrid and trihybrid crosses, there are exceptions to Mendelian principles, i.e. the occurrence of different phenotypic ratios. The more complex patterns of inheritance are the extensions of Mendelian Genetics. There are examples where phenotype of the organism is the result of the interactions among genes. Gene interaction – A single phenotype is […]
The protein called starch branching enzyme (SBEI) is encoded by the wild-type allele of the gene (RR) which is dominant. When the seed matures, this enzyme SBEI catalyzes the formation of highly branched starch molecules. Normal gene (R) has become interrupted by the insertion of extra piece of DNA (0.8 kb) into the gene, resulting […]
Pollination provides information about evolution, ecology, animal learning and foraging behaviour. Flowers not only supply nectar but also provide microclimate, site and shelter for egg laying insects. The association of insects benefits the flower by getting pollinated and ensures the propagation of its own progeny. The floral parts are well modified in shape, size to […]
Dr. Panchanan Maheshwari was an eminent botanist specialising in plant embryology, morphology and anatomy, plant physiology and biochemistry. He was one of the leading plant biologists who established the technique of test-tube fertilization of angiosperms. Another landmark discovery by Dr. Maheshwari was production of haploids using anther culture. This discovery initiated a new era in […]
Test cross Test cross is crossing an individual of unknown genotype with a homozygous recessive. In Mendel’s monohybrid cross all the plants are tall in F1 generation. In F2 tall and dwarf plants were in the ratio of 3:1.Mendel self pollinated dwarf F2 plants and got dwarf plants in F3 and F4 generations. So he […]
Mendel chose two contrasting traits for each character. So it seemed logical that two distinct factors exist. In F1 the recessive trait and its factors do not disappear and they are hidden or masked only to reappear in ¼ of the F2 generation. He concluded that tall and dwarf alleles of F1 heterozygote segregate randomly […]
(a) Rowlatt Act It was as part of the British policy of ‘rally the moderates and isolate the extremists’ that the Indian Councils Act 1919 and the Rowlatt Act of the same year were promulgated. T hroughout the World War, the repressive measures against the terrorists and revolutionaries had continued. Many of them were hanged […]
Montagu–Chelmsford Reforms Edwin Montagu and Chelmsford, the Secretary of State for India and Viceroy respectively, announced their scheme of constitutional changes for India which came to be known as the Indian Councils Act of 1919. The Act enlarged the provincial legislative councils with elected majorities. The governments in the provinces were given more share in […]
Introduction Mohandas Karamchand Gandhi was born in the coastal town of Porbandar in 1869. When he returned to India in 1915 he had a record of fighting against inequalities imposed by the racist government of South Africa. Gandhi certainly wanted to be of help to forces of nationalism in India. He was in touch with […]
Rise of Labour Movement Introduction of machinery, new methods of production, concentration of factories in certain big cities gave birth to a new class of wage earners called factory workers. In India, the factory workers, mostly drawn from villages, initially remained submissive and unorganised. Many leaders like Sorabjee Shapoorji and N.M. Lokhanday of Bombay and […]
The Defence of India Act, 1915 Also referred to as the Defence of India Regulations Act, it was an emergency criminal law enacted with the intention of curtailing the nationalist and revolutionary activities during the First World War. The Act allowed suspects to be tried by special tribunals each consisting of three Commissioners appointed by […]
Monohybrid Cross Monohybrid inheritance is the inheritance of a single character i.e. plant height.It involves the inheritance of two alleles of a single gene. When the F1 generation was selfed Mendel noticed that 787 of 1064 F2 plants were tall, while 277 of 1064 were dwarf. The dwarf trait disappeared in the F1 generation only […]
Impact of the War During the years prior to First World War the political condition of the India was in disarray. In order to win over the “Moderates” and the Muslim League with a view to isolating the “Extremists” the British passed the MintoMorley Reforms in 1909. The Moderates observed a policy of wait and […]
All India Home Rule League We may recall that many foreigners such as A.O. Hume had played a pivotal role in our freedom movement in the early stages. Dr Annie Besant played a similar role in the early part of the twentieth century. Besant was Irish by birth and had been active in the Irish […]
Introduction Several events that preceded the First World War had a bearing on Indian nationalist politics. In 1905 Japan had defeated Russia. In 1908 the Young Turks and in 1911 the Chinese nationalists, using Western methods and ideas, had overthrown their governments. Along with the First World War these events provide the background to Indian […]
Terminology related to Mendelism Mendel noticed two different expressions of a trait – Example: Tall and dwarf. Traits are expressed in different ways due to the fact that a gene can exist in alternate forms (versions) for the same trait is called alleles.If an individual has two identical alleles of a gene, it is called […]
Mendel’s theory of inheritance, known as the Particulate theory, establishes the existence of minute particles or hereditary units or factors, which are now called as genes. He performed artificial pollination or cross pollination experiments with several true-breeding lines of pea plants. A true breeding lines (Pure-breeding strains) means it has undergone continuous self pollination having […]
Mendelism The contribution of Mendel to Genetics is called Mendelism. It includes all concepts brought out by Mendel through his original research on plant hybridization. Mendelian genetic concepts are basic to modern genetics. Therefore, Mendel is called as Father of Genetics. Father of Genetics – Gregor Johann Mendel (1822 – 1884) The first Geneticist, Gregor […]
Reproduction involving fertilization in flowering plants is called amphimixis and wherever reproduction does not involve union of male and female gametes is called apomixis. The term Apomixis was introduced by Winkler in the year 1908. It is defined as the substitution of the usual sexual system (Amphimixis) by a form of reproduction which does not […]
Genetics – The Science of heredity (Inheritance) “Genetics” is the branch of biological science which deals with the mechanism of transmission of characters from parents to offsprings. The term Genetics was introduced by W. Bateson in 1906. The four major subdisciplines of genetics are 1. Transmission Genetics / Classical Genetics – Deals with the transmission […]