It is a common knowledge that after sexual reproduction, the resulting offspring tends to look like their parents in one way or the other. This resemblance may be related to the immediate parents or even to the grand parents. This tendency of the offspring to look like their parents or grand parents is a phenomenon which goes on from generation to generation. This is due to certain characters or traits which the offspring have inherited from their parents this confirming one of the fundamental observations about heredity made by men several thousand years ago, that is “like tends to begat like”.
Very often in our homes such questions are asked about inheritance of traits such as complexion, colours of eyes and hair possess by individuals. Also, out of many children in a family, a particular child may be described as exhibiting some traits pertaining to one of the grand parents. When questions of this nature arises, one is actually asking genetic questions.
So what then is Genetics?
Genetics may then be described as the branch of biological science that deals with questions and answer on inheritance which include traits or characters such as height, complexion, colour of hair and eyes etc, which are transmitted from parents to offspring during sexual reproduction. The ways and manners through which these characters are inherited from parents is known as heredity.
History of Genetics
The study of genetics dates back to several years in man’s curiosity to unravel the mechanism for the transmission of traits from parents to offspring. A breeder called Kilreuter worked with tobacco plants about 1770. He made crosses with different varieties of plants and produce hybrids. He also recognized that parental characters were transmitted by both the pollen and the ovule. However, studies of heredity before 1866 were not conclusive. The results obtained by earlier investigations offered little explanation of the way inheritable features were transmitted from one generation to the other.
Work in genetics continued to draw the attention of natural scientists, and in the year 1866, an Australian monk who lived in the monastry in Brun, published two small treaties on the laws of heredity in the journal of the local natural science society. This man was Gregor Mendel. He later became the head of the monastery. His many added responsibilities prevented him from continuing his study of heredity. He died in 1886 without realising that his two little contributions could form the foundation for all the work that has since been done in genetics.
Gregor Mendel: The father of Genetics
It was not until 1900 that three investigators working independently discovered what they thought were new findings about heredity. These men were de Vries in Holland, Correns in Germany, and Von Tschermak in Australia. They discovered the phenomenon of regular, predictable bratios of the types of offspring produced by mating pure breeding parents. But, then, searching through literature in the field, they came across Mendel’s earlier reports on the same subject. They then realised bthat Mendel was the pioneer in these investigations and gave him full credit for his work by naming two of the fundamental principles of heredity Mendel’s laws. All the work that has been done in genetics has made use of Mendel’s basic discoveries, and so, today, he is known as the father of modern genetics. Great advances have been made in genetics, cytogenetics and related fields but Mendel’s two laws still remain the fundamental laws of heredity in genetics.
Various Branches of Genetics
A sketch on the Branches of Genetics
Classical genetics: consists of the technique and methodologies of genetics that predate the advent of molecular biology. A key discovery of classical genetics in eukaryotes was genetic linkage. The observation that some genes do not segregate independently at meiosis broke the laws of Mendelian inheritance, and provided science with a way to map characteristics to a location on the chromosomes.
Quantitative genetics: s the study of continuously measured traits (such as height or weight) and their mechanisms. It can be an extension of simple Mendelian inheritance in that the combined effects of one or more genes and the environments in which they are expressed give rise to continuous distributions of phenotypic values.
Biochemical genetics: the study of the fundamental relationships between genes, protein, and metabolism.
This involves the study of the cause of many specific heritable diseases
Cytogenetics: is a branch of genetics that is concerned with the study of the structure and function of the cell,
especially the chromosomes
Behavioural genetics: is the field of study that examines the role
of genetics in animal (including human) behaviour.
Developmental genetics is the study of the process by which organisms grow and develop
Conservation genetics: is an interdisciplinary science that aims to apply genetic methods to the conservation
and restoration of biodiversity
Ecological genetics: is the study of genetics in natural populations.
Genetic engineering: is the direct manipulation of an organism’s genome using biotechnology.
New DNA may be inserted in the host genome by first isolating and copying the genetic material of interest using molecular cloning methods to generate a DNA sequence, or by synthesizing the DNA, and then inserting this construct into the host organism.
Metagenics: is the practice of engineering organisms to create a specific enzyme, protein, or other biochemicals from simpler starting materials. The genetic engineering of E. coli with the specific task of producing human insulin from starting amino acids is an example.
Genomics: is a discipline in genetics that applies recombinant DNA, DNA sequencing methods, and bioinformatics to sequence, assemble, and analyze the function and structure of genomes (the complete set of DNA within a single cell of an organism
Human genetics: is the study of inheritance as it occurs in human beings. Human genetics encompasses a
variety of overlapping fields including: classical genetics, cytogenetics, molecular genetics, biochemical genetics, genomics, population genetics, developmental genetics, clinical genetics and genetic counselling.
Medical genetics: is the specialty of medicine that involves the diagnosis and management of hereditary disorders. Medical genetics differs from Human genetics in that human genetics is a field of scientific research that may or may not apply to medicine, but medical genetics refers to the application of genetics to medical care.
Microbial genetics: This involves the study of the genotype of microbial species and also the expression system in the form of phenotypes. It also involves the study of genetic processes taking place in these micro organisms i.e., recombination etc.
Molecular genetics: is the field of biology and genetics that studies the structure and function of genes at a molecular level. Molecular genetics employs the methods of genetics and molecular biology to elucidate molecular function and interactions among genes. It is so-called to differentiate it from other sub fields of genetics such as ecological genetics and population genetics.
Population genetics: is the study of allele frequency distribution and change under the influence of the four main evolutionary processes: natural selection, genetic drift, mutation and gene flow. It also takes into account the factors of recombination, population subdivision and population structure. It attempts to
explain such phenomena as adaptation and speciation.
Psychiatric genetics: is a subfield of behavioral neurogenetics, studies the role of genetics in psychological conditions such as alcoholism, schizophrenia, bipolar disorder, and autism. The basic principle behind psychiatric genetics is that genetic polymorphisms, as indicated by linkage to e.g. a single nucleotide
polymorphism (SNP), are part of the etiology of psychiatric disorders.
Importance of Genetics
Diseases and Treatments
Forensics and Legal Implications
Stay connected to myschoollibrary for more educational contents