Hello All AIPMT Biology Aspirants, here is the study material of Genetics.
- Genetics: It is the science of heredity and variation.
- Heredity: Transmission of traits from parents to offspring via genetic information.
- Variation: In biology, the occurrence of differences among individuals.
- Character: Heritable feature/ attribute that varies among individuals is called character, such as eye color.
- Trait: Variants of character in an individual, e.g. eye color is a character; while variation in eye color i.e. brown eyes or blue eyes are traits. or Trait is a characteristic that has alternative forms, such as different blood groups in human. Blood group is a character and types of blood group A, B, O, AB are traits.
- DNA: Deoxyribonucleic acid; Information-carrying genetic material that comprises the genes.
- Gene: A section of DNA or RNA that carries hereditary information for building one or more related polypeptides.
- Gene is a hereditary factor that influences a particular trait. Gene is the basic unit of heredity.
There are three major areas of Genetics: Classical Genetics, Molecular Genetics, and Evolutionary Genetics.
- Classical genetics deals with chromosomal theory of inheritance; that is, the concept that genes are located in a linear fashion on chromosomes. It includes the study of Mendel’s principles, Meiosis and mitosis, Sex determination, Sex linkage, Chromosomal mapping, Cytogenetics (chromosomal changes).
- Molecular genetics is the study of the genetic material: its structure, replication, and expression, such as structure of DNA, its transcription, translation, DNA cloning and genomics, Control of gene expression, DNA mutation and repair, extrachromosomal inheritance.
- Evolutionary genetics is the study of the mechanisms of evolutionary change, or changes in gene frequencies in populations. Darwin’s concept of evolution by natural selection is studied in this area of the study of inheritance.
- In the middle of the Eighteenth century, 3 scientists, Linnaeus , Kolreuter, Gaertner performed artificial cross pollinations in plants and obtained hybrid offspring. Their observations were similar to those of Mendel, but they were not able to interpret them correctly.
- Kolreuter worked on Tobacco plant; Gartner worked on Garden Pea and Maize.
- Elaborating Kolreuter work, Knight worked on Garden Pea.
INTRODUCTION OF MENDEL
- Gregor Johnn Mendel (1822–1884) was an Austrian monk in Brunn, Austria. He was born in one of the peasant families settled in the Czech village of Heinzendorf, part of Austria.
- In 1847 he became a priest, adopting the clerical name Gregor. He subsequently taught at the local high school, taking time out between 1851 and 1853 to study at the University of Vienna. After returning to Brünn, he resumed his life as a teaching monk and began the genetic experiments that eventually made him famous.
- He completed his experiments with peas in 1864. In 1865, Mendel presented the results to Natural History Society of Brunn, and the following year, he published a detailed report in the society’s proceedings.
- Mendel’s ideas, published in 1866 under the title “Experiments in Plant Hybridization,” (In German- “Versuche Uber Pflanzen-Hybriden”) which explained how the characteristics of organisms are inherited.
- Unfortunately, Mendel’s paper remain unnoticed for 35 years, until 1900, when it was rediscovered by three botanists working independently—Hugo de Vries in Holland, Carl Correns in Germany, and Eric von Tschermak in Austria.
- William Bateson coined a new term “Genetics” to describe the study of heredity, which means “to generate.”
- Year 1900 is considered to represent the birth year of modern Genetics.