GENETICS AND EVOLUTION

Evolution is the method by which populations of organisms change over generations. Genetic variations come under these changes. Genetic variations can arise from variants of genes which are also called mutations or from a general process in which genetic material is rearranged as a cell is getting ready to divide known as genetic recombination.

Genetic variations that change gene activity or protein function can show different characteristics in an organism. If a character is advantageous and helps the individual for survival and reproduction, the genetic variation is more likely to be carried to the next generation which is a process known as natural selection.

With passage of time, as generations of individuals with the same characteristics continue to reproduce, the characteristics which are advantageous become increasingly common in a population, making the population different from that of an ancient one. The population sometimes becomes so different that it is considered a new species.

GENETICS 

Genetics relates to the branch of biology which is the study of heredity and how qualities and characteristics are passed on from one generation to another by means of genes. 

Genetics arises from identification of genes which are the fundamental units responsible for heredity. Genetics may be defined as the study of genes at various levels, including the level in which they act in the cell and the level in which they are transferred from parents to offspring.

Modern genetics concentrates on the chemical substance that genes are made of, called deoxyribonucleic acid, or DNA. DNA affects the chemical reactions that comprises the living processes within the cell. Genetics as a scientific discipline came out from the work of Sir Gregor Mendel back in the middle of the 19th century. 

Mendel suspected that traits were inherited as individual units, and although he was unaware of the physical or chemical nature of genes at that time, his units became the basis for the development of the understanding of heredity now. The word genetics was introduced in 1905 by English biologist William Bateson who was one of the discoverers of Mendel’s work and who became an expert of Mendel’s principles of inheritance.

EVOLUTION

Evolution may be defined as a change in the genetic composition of a population over continuing generations. The Theory of Evolution by natural selection was first introduced in the book ‘On the Origin of Species’ written by Sir Charles Darwin published in the year 1859.

Darwin in this book has described how organisms evolve over generations through the inheritance of physical or behavioral characteristics. The theory starts with the point where within a population, there is change in characteristics. 

According to the theory, individuals with characteristics that enable them to adapt to their environments will help them in survival and have more generations which will inherit those habits. Individuals which adapt less habits will survive less commonly to pass them on to their next generations. With passing of time, the characteristics that enable species for survival and reproduction will become more common in the population and the population will change or evolve. 

GENETIC EVOLUTION

Evolutionary genetics is the study of how change in genetic composition is controlled by genetic variation. It includes topics such as the evolution of genome structure, the genetic basis of speciation and adaptation, and genetic change within populations. 

Evolution occurs when these hereditary differences become more general in a population, either non-randomly through natural selection or randomly through genetic drift. This occurs because organisms with advantageous characteristics pass on more of these heritable habits to the next generation.

Over many generations, adaptations occur through a combination of continuous, small, general changes in characters, and natural selection of those changes which are best-suited for their environment.

PROCESS OF EVOLUTION

Genetic Evolution can be processed through mechanisms namely, natural selection, genetic drift, gene flow and mutation bias. 

Natural selection

Evolution by natural selection is the process by which habits that enhance survival and reproduction become very common in continuing generations of a population. Natural selection most generally makes nature the measure against which individuals and individual characteristics are more or less likely to survive.

‘Nature’ here refers to an ecosystem, a system in which organisms interact with different element, physically as well as biologically, in their local environment. Natural selection can act at different levels of organization, such as genes, cells, individual organisms, groups of organisms and species. Selection can act at multiple levels.

Genetic drift

Genetic drift is the random changes of frequencies of genes within a population from one generation to the next generation. When selective forces are absent or relatively weak, gene frequencies are equally likely to drift upward or downward at each continuous generation because the genes are subject to error of sampling. This drift stops when a gene eventually becomes constant, either by vanishing from the population or replacing the other genes entirely.

Genetic drift may therefore remove some genes from a population. Even in the absence of selective forces, genetic drift can cause two separate populations that began with the same genetic structure to drift apart into two divergent populations with different sets of genes.

Gene flow

Gene flow involves the exchange of genes between populations and between species. The presence or absence of gene flow changes the method of evolution. Due to organisms being complex, any two completely isolated populations will eventually evolve genetic incompatibilities through neutral processes, even if both populations remain similar in terms of their adaptation to the environment.

If genetic differentiation between populations develops, gene flow between populations can introduce characteristics or genes which are disadvantageous in the local population. This may lead to organisms within these populations evolving in processes that prevent mating with genetically distant populations, eventually bringing the appearance of new species in the environment.

Mutation bias

The concept of mutation bias is seen in several scientific contents, most commonly in molecular studies of evolution, where mutation biases may be invoked to account for such phenomena as genome composition between species. In cancer research, some types of tumors have distinctive characteristic combination of mutation types that reflect differences in the contributions of mutational pathways. Mutational signatures have proved useful in both detection and treatment of cancer.

When mutation bias is invoked as a possible cause of some pattern of asymmetry in evolution, the alternative methods may include selection, biased gene conversion, and demographic factors.

CONCLUSION

In this article, we have discussed the definition of genetics and evolution. To conclude, we have learnt about the evolution of genetics over generations. Moreover, some related terms  such as Gene FLow, Mutation Bias and Genetic Drift are also explained so that you will get a clear concept about everything.  We have learnt about how heredity is followed by generations over years and also, we got to know how common traits are observed among populations.