BRANCHES OF GENETICS

Now a days the science of genetics has proliferated into numerous distinctive subdisciplines.
Some of the significant branches of genetics are the following :
1. Plant genetics. The genetics of plants.
2. Animal genetics. The genetics of animals.
3. Human genetics. It involves the study of heredity of human traits, human disorders, betterment and correction of human disorders.
4. Microbial genetics. It deals with the genetics of microorganisms (viz., viruses, bacteria, unicellular plants and animals).
5. Fungal genetics or mycogenetics. The genetics of fungi.
6. Viral genetics. Genetics of virus.
7. Drosophila genetics. Genetics of fruit fly, Drosophila sp.
8. Mendelian genetics. It involves study of heredity of both qualitative (monogenic) and quantitative (polygenic) traits and the influence of environment on their expressions.
9. Quantitative genetics. It involves the study of heredity of quantitative traits such as height, weight and IQ in human beings and milk production in cattle.
10. Morganian genetics. It includes study of recombination (crossing over) in all kinds of organisms such as higher plants, animals, fungi, bacteria and viruses. It also involves the preparation of linkage maps of chromosomes.
11. Non-Mendelian genetics. It involves a study of the role of cytoplasm and its organelles (particularly chloroplasts and mitochondria) in heredity.
12. Mutations. They involve study of heredity of both chromosomal changes (structural and numerical) and also gene mutation.
13. Cytogenetics. It provides the cytological explanations of different genetical principles.
14. Molecular genetics. It includes the study of structure and function of gene and regulation of its activity.
15. Transmission genetics. It includes the study of mode of gene transmission from generation
to generation. The kind of studies that Mendel performed are now included in the discipline of transmission genetics.
16. Clinical genetics. Genetics involved in the detection of causes of diseases such as haemophilia, colour blindness, diabetes, phenylketonuria.
17. Immunogenetics. It deals with genetics of production of different types of antibodies; the diversity of antibodies has been found to be under control of genetic regulation.
18. Behavioural genetics. It involves the interaction of genes with the environment to produce a particular pattern of behaviour. In Drosophila many behaviour genes have been identified, e.g., mutants described as sluggish, non-climbing, flightless, easily shocked, etc., and genes regulating sexual behaviour. In primates including humans, it has been found that IQ (intelligence quotient) is governed by genetics (parentage), environment (adopted parents) and developmental stage (age) of an individual.
19. Forward genetics and reverse genetics. During the last decade, the term reverse genetics has been used for physical mapping and isolation of genes whose protein products are unknown. The term forward genetics has been used for genes which are mapped on the basis of phenotype (or gene product or protein), using the technique of classical genetics. However, recently in 1991, the term reverse genetics has been redefined by Paul Berg (Nobel Laureate). According to him, the term reverse genetics should be restricted to those studies, where we start the study with a DNA segment with unknown phenotypic effect, introduce this DNA (without any alteration or other modification) into a plant or an animal and then follow the phenotype.