INTRODUCTION
The field of anthropology is basically concerned with both biological and social/ cultural evolution as well as diversity of human population throughout the ages. For understanding human genetics one needs to understand about physical anthropology or biological anthropology which deals with the study of human biology, evolution of the human organism, the relation between environment and human organism, and genetic variations between individuals and groups. The field of human genetics (of anthropological interest may be referred to as anthropological genetics which is concerned with human population variation study) uses pattern of genetic similarity and differences among different human populations throughout the human ancestry to infer the history of human evolution, migration, admixture and diversity. This would enable the scientists in explaining how the modern Homo sapiens evolved through the stages of Homo habilis and Homo erectus through the millennia to the modern man and the reasons behind many of the biological differences that we observe in different ethnic groups of the world.
| Genetics is a branch of biology that deals with heredity or inherited variation of genetic traits. The science of genetics studies the phenotypic (visible) differences between individuals and attempts to relate them to underlying genic or chromosomal differences. The hereditary units that are transmitted through parent to offspring are called genes. |
The word ‘gene’ is used frequently in genetics as a designation for each of the small units of heredity within a cell. Genetics has proved to have numerous practical applicatons because man has learned to use the discoveries in many diferent fields. It is being used in such diverse areas as plant and animal breeding, medical diagnosis, and genetic counseling, and even in cases of law. Genes are biochemical instructions that are supposed to determine those inherited traits that reside in the long molecules of deoxyribonucleic acid or DNA. Long polynucleotide molecules of deoxyribonucleic acid, called DNA, are intimately assocaited with chromosmes and are found exclusively in chromosomes. The chemical composition of chromosomes includes histones, proteins and deoxyribonecleic acid. The DNA is found only in chromosomes and is double stranded. The genes are then, sections of the DNA ladder-like molecules; different genes are different because they contain different sequence of the “letters’ A, T, C, and G. DNA in conjunction with protein matrix may form nucleoprotein and becomes organised as chromosomes that are found in the nucleus of the cell. DNA is a stable molecule, however, on rare occasions a change or heritable alteration may occur spontaneously, is called mutation which is the lead sources of biological variation. In the study of heredity, we must clearly distinguish between ‘genes’and ‘traits’. Genes are at the bottom of developemnt. On the other hand, traits, such as hair colour, eye colour, size, shape, etc. are end products of development. They require both the proper genes and proper environment for their development.
HISTORY, DEFINITION AND SCOPE
Human Genetics, as the name indicates, describes the study of inherited variation as it occurs in human beings. The inheritance of many traits, including human traits is at present fairly well known. The biochemical studies on the constituents of the chromosomes have given essentially the correct picture how heredity really works at the molecular level. Genes can be the common factor of the most inherited traits. Genes have become prominent in the nature versus nurture debate. Study of human genetics can be useful as it can answer questions about human nature, behaviour as well as understand the diseases and disease treatment, and genetics of human life.
The science of genetics emerged from the famous work of Father Gregor Mendel (1822-1884) while working at the Augustinian monastery of St Thomas at Bruno in Moravia with the common garden pea. He published the results of his studies in 1866 and thereby laid the foundation of modern genetics. In his paper, Mendel proposed some basic genetic principles — the law of segregation, and the law of independent assortment. The first one states that each parent contains two copies of a unit of inheritance (later called gene), however, any one of two genes (called allele) can be transmitted to the offspring through the gamete. Which allele in a parent’s pair of alleles is inherited is a matter of chance. The second principle states that the segregation of such gene pair (allele) occurs independently in respect of other gene pair, i.e. the paired genes (allelic pairs) separate from oneanother and are distributed to dif ferent sex cells. The result is that new combinations of genes present in neither parent are possible. However, during his (Mendel) lifetime very few people realised the importance of his path breaking research. In 1901, Hugo de Vries, Carl Correns and Erich von Tschermak realised that Mendel’s observations, conclusions and hypothesis have great importance in the field of genetics. During early 1900s, researchers noted that chromosomes behave like Mendel’s traits and also inherited in random combinations. In 1909 Wilhelm Johansen renamed Mendel’s characters as ‘gene’ and William Bateson coined the term ‘genetics’ to study genes. Thereafter researchers repeated and confirmed Mendel’s hypothesis and his (Mendel) ideas on the inheritance of traits became more widely accepted and is now termed as Mendel’s laws of inheritance.
Another milestone in the field of genetics is the discovery of the model for the structure of DNA as a genetic material by J.D. Watson and F.H.C. Crick in 1953. This was probably the key stone that unlocked an explosion in the field of human genetics as a form of molecular revolution.
Following are some of the fields where human genetics may contribute its knowledge for the betterment of the human society.
- To understand basic principles of inherited variation in man and to understand application of genetics in human life, and
- To answer questions about human nature, understand the diseases and development of effective disease treatment and health care.