10 public questions tagged with this topic.
Friedrich Miescher first isolated DNA in 1869 and named it ‘Nuclein’. This follows from NCERT principle where the relation explains the outcome clearly for students in simple steps.
Ref: NCERT Biology Textbook for Class XI and XII (Botany section), Chapter: Morphology and Anatomy of Flowering Plants, Topic: Plant structure and tissue systems.
Dolly cloning breakthrough credited to Ian Wilmut and Keith Campbell at Roslin Institute, Edinburgh, working with embryologist Bill Ritchie. Wilmut led somatic cell nuclear transfer project aiming to produce transgenic sheep for pharmaceutical protein production in milk. Using cell cycle synchronization inducing quiescence in donor mammary cells and electrical fusion with enucleated oocytes, team generated viable lamb. Published in Nature 1997, work demonstrated differentiated mammalian nucleus could be reprogrammed completely. Gurdon, Briggs, King pioneered amphibian cloning earlier; Aristotle founded ancient embryology but not associated with modern cloning methodologies.
Ref: Campbell et al., Nature 1996; Gilbert, 12th ed., Chapter 3: Wilmut and Dolly cloning.
Early electron microscopy after osmium fixation revealed trilaminar image of membranes about 7.5 nm thick: two dark lines 2 nm each representing protein stained by osmium, light core of lipid. J. David Robertson at Harvard analyzed myelin, chloroplast, and plasma membranes and in 1959 proposed Unit Membrane Model asserting all biological membranes share same basic construction of lipid bilayer sandwiched between non-lipid layers, with asymmetry that inner and outer surfaces differ chemically, explaining functional polarity. Robertson emphasized continuity of membranes through ER and nuclear envelope and suggested proteins extended as sheets. This unified view improved over Davson-Danielli paucimolecular sandwich which proposed protein layers without EM proof, and provided terminology unit membrane widely used in histology. Although later Singer and Nicolson showed proteins are globular amphipathic entities embedded within fluid lipid phase rather than extended coats, Robertson's model was pivotal for recognizing universal bilayer organization and inspiring later fluid mosaic concept, placing bilayer as central architectural principle.
Ref: Alberts et al., Molecular Biology of the Cell, 7th ed., Chapter 10: Unit Membrane Model, Robertson.
Louis Pasteur demonstrated that life does not originate spontaneously but comes from pre-existing life.
Ref: NCERT Class 12 Biology Chapter 6: Evolution Origin of Life - Theories Miller Urey Experiment
Frederick Griffith discovered the phenomenon of transformation while working with Streptococcus pneumoniae.
Ref: NCERT Class 12 Biology Chapter 5: Molecular Basis of Inheritance Search for Genetic Material and RNA World
Carl Woese proposed the RNA World Hypothesis, which suggests that RNA was the first genetic material.
Ref: NCERT Class 12 Biology Chapter 5: Molecular Basis of Inheritance Search for Genetic Material and RNA World
Henking discovered the X-chromosome while studying insect spermatogenesis.
Ref: NCERT Class 12 Biology Chapter 4: Principles of Inheritance and Variation Chromosomal Theory Linkage Recombination Gene Mapping
Thomas Hunt Morgan worked on Drosophila and discovered linkage and recombination.
Ref: NCERT Class 12 Biology Chapter 4: Principles of Inheritance and Variation Chromosomal Theory Linkage Recombination Gene Mapping
Sutton and Boveri proposed the Chromosomal Theory of Inheritance, linking Mendel’s principles to chromosome behavior.
Ref: NCERT Class 12 Biology Chapter 4: Principles of Inheritance and Variation Chromosomal Theory Linkage Recombination Gene Mapping
Sutton and Boveri proposed the chromosomal theory of inheritance, linking chromosomes to Mendel’s principles.
Ref: NCERT Class 12 Biology Chapter 4: Principles of Inheritance and Variation Chromosomal Theory Linkage Recombination Gene Mapping
