Natural selection and genetic modification study guide

Genetic engineering is the process of deliberately modifying an organism's DNA using biotechnology. The main stages involve isolating a desired gene using restriction enzymes, which cut DNA at specific sequences, often creating sticky ends. At the same time, a vector such as a bacterial plasmid is cut with the same restriction enzyme to ensure compatible sticky ends. The gene and vector DNA fragments are then joined together using DNA ligase, an enzyme that forms strong bonds between their sugar-phosphate backbones. The recombinant DNA (vector plus new gene) is introduced into a host cell, such as a bacterium or plant cell, where it can be replicated and the new gene can be expressed.

Tissue culture is a vital biotechnological technique used to grow cells, tissues, or organs in an artificial environment separate from the organism. This process relies on the principle that plant cells are totipotent, meaning a single plant cell can regenerate an entire plant. For animal cells, the technique is used to grow specific cell lines, often for research or medical purposes. The process typically involves taking a small piece of tissue, known as an explant, sterilizing it, and then placing it in a nutrient-rich medium containing growth regulators. Under controlled conditions of temperature, light, and humidity, the explant proliferates, forming a mass of undifferentiated cells called a callus. This callus can then be induced to differentiate and form whole plants or specific cell lines. This method offers significant advantages in medical research, such as drug testing and producing vaccines, and in plant breeding programmes for rapid clonal propagation of desirable varieties, disease eradication, and genetic modification.