How are tissues and organs different?

In layman's terms how do we get to functinal organs starting from DNA? Such as DNA (Definition...)---> Proteins (Definition..)  ------> XXXXX -------> YYYYYY -----> Tissues (Definition...) -----> Organs?

• Answer:

  In short: DNA contains the information needed to make proteins. Proteins have different functions, many of them are able to react to changes in the cellular environment. Tissue and organ functions are regulated via the communication between cells, which is mainly carried out by a set of highly specialized proteins working together. The DNA does not 'know' about the organs, almost all functions are carried out by proteins. It is one of the basic principles in life sciences that the higher you go in the level of organization, the more complexity you see. An organ can accomplish things that a tissue couldn't, and DNA could be considered as the most basic level of organization here. Imagine DNA to be the 'blueprints' for everything that is needed to build the entire organism. It reads like a loooooooong instruction manual, written in a language we call the 'genetic code' and using an alphabet of only four letters, the nucleotides that differ in which one of the four bases adenine(A), cytosine(C), guanine(G) and thymine(T) they carry. In the sequence of the DNA, there are regions that code for proteins, we call them protein coding genes (there are also genes that code for something that is not proteins, but let's concentrate on the proteins for now). Through a process called gene expression, proteins are made from the genes in the DNA sequence. The main function of DNA is to store the genetic information of the cell. Different proteins, on the other hand, have many different functions. There are structure proteins that help stabilize the form of the cell, there are enzymes that carry out specific reactions for the metabolism or for the replication of the cell, and there are proteins called receptors. These receptors are transported to the cell membrane after they have been synthesized. They are important in the communication between cells in a tissue or between tissues. A tissue is an amount of cells of the same kind (muscle cells, or fat cells, or skin cells, ...) and an organ can consist of various tissues, it is defined by the major function it has in the organism. Both tissues and organs work because the cells that make them up communicate with each other, as well as with other tissues or organs. And most of this communication is carried out by specialized proteins. For instance, a certain enzyme in one cell synthesizes a signal molecule. This is transported to the cell membrane, brought out of the cell through the membrane, and sent to another cell. There, it can bind to a receptor protein that is specifically designed for this signal molecule, and the receptor/signal molecule binding will trigger the appropriate response in that cell. And that is, basically, how cells communicate. Which genes are transcribed next, and how much of the resulting proteins is needed, is regulated mostly by proteins too. The DNA itself has no regulatory influence on the organization and function of the organ, tissue, or even the cell. DNA is the blueprints, almost everything that is 'done' is done by proteins.