Genetic engineering have specialisations related to plants, animals and human beings. Genetic engineering in plants and animals may be to improve certain natural characteristics of value, to increase resistance to disease or damage and to develop new characteristics etc. It is used to change the colour, size, texture etc of plants otherwise known as GM (Genetically Modified) foods. GE in humans can be to correct severe hereditary defects by introducing normal genes into cells in place of missing or defective ones.
A cell is the smallest living unit, the basic structural and functional unit of all living matter, whether a plant, an animal, humans or a fungus. While some organisms are single celled, others like plants, animals, humans etc are made up of a lot more cells. For eg humans have approximately 3 million cells. A cell is composed of a 'cell membrane' enclosing the whole cell, many 'organelles' equivalent to the organs in the body and a 'nucleus' which is the command centre of the cell.
Inside the nucleus are the chromosomes which is the storage place for all genetic (hereditary) information which determines the nature and characteristics of an organism. This information is written along the thin thread, called DNA, a nucleic acid which constitutes the genes (units of heredity). The DNA governs cell growth and is responsible for the transmission of genetic information from one generation to the next.
Genetic engineering aims to re-arrange the sequence of DNA in gene using artificial methods. The work of a genetic engineer involves extracting the DNA out of one organism, changing it using chemicals or radiation and subsequently putting it back into the same or a different organism. For eg: genes and segments of DNA from one species is taken and put into another species. They also study how traits and characteristics are transmitted through the generations, and how genetic disorders are caused. Their research involves researching the causes and discovering potential cures if any.