I'm not sure I understand this question. Can you elaborate.

1) "A phenotype is any observable characteristic or trait of an organism: such as its morphology, development, biochemical or physiological properties, or behavior. Phenotypes result from the expression of an organism's genes as well as the influence of environmental factors and possible interactions between the two. The genotype of an organism is the inherited instructions it carries within its genetic code. Not all organisms with the same genotype look or act the same way, because appearance and behavior are modified by environmental and developmental conditions. Similarly, not all organisms that look alike necessarily have the same genotype. This genotype-phenotype distinction was proposed by Wilhelm Johannsen in 1911 to make clear the difference between an organism's heredity and what that heredity produces. The distinction is similar to that proposed by August Weismann, who distinguished between germ plasm (heredity) and somatic cells (the body). A more modern version is Francis Crick's Central dogma of molecular biology. Despite its seemingly straightforward definition, the concept of the phenotype has some hidden subtleties. First, most of the molecules and structures coded by the genetic material are not visible in the appearance of an organism, yet they are observable (for example by Western blotting) and are thus part of the phenotype. Human blood groups are an example. So, by extension, the term phenotype must include characteristics that can be made visible by some technical procedure. Another extension adds behaviour to the phenotype since behaviours are also affected by both genotypic and environmental factors. Second, the phenotype is not simply a product of the genotype, but is influenced by the environment to a greater or lesser extent (see also phenotypic plasticity). And, further, if the genotype is defined narrowly, then it must be remembered that not all heredity is carried by the nucleus. For example, mitochondria transmit their own DNA directly, not via the nucleus, though they divide in unison with the nucleus." Source and further information: http://en.wikipedia.org/wiki/Phenotype Further information: http://en.wikipedia.org/wiki/Heredity 2) "Gene expression is the process by which information from a gene is used in the synthesis of a functional gene product. These products are often proteins, but in non-protein coding genes such as rRNA genes or tRNA genes, the product is a functional RNA. Several steps in the gene expression process may be modulated, including the transcription step and translation step and the post-translational modification of a protein. Gene regulation gives the cell control over structure and function, and is the basis for cellular differentiation, morphogenesis and the versatility and adaptability of any organism. Gene regulation may also serve as a substrate for evolutionary change, since control of the timing, location, and amount of gene expression can have a profound effect on the functions (actions) of the gene in the organism." Source and further information: http://en.wikipedia.org/wiki/Gene_expression Further information: http://en.wikipedia.org/wiki/Genetics

The living cell is a miracle of biochemical wonders. DNA is a long chain-like molecule made of 4 different kinds of links, abbreviated A, T, G and C. The "letters of the genetic code" also hook up to one another between chains like this: A pairs with T and G pairs with C. Each long chain of DNA is a double stranded chain of made of A's T's G's and C's in an order that is the genetic code ( order of nucleotides). The double DNA chain can untwist and make an identical copy on each side, A sticking to T and G to C, so one DNA can replicate into two copies identical in code. Then the DNA code can be copied onto messenger RNA by the same pairing scheme, A goes with T, C with G, except RNA has U instead of T. (complementary base pairing) The genetic code, now on the RNA, is read, three letters at a time, with each triplet "codon" coding for one of the twenty or so amino acid "beads" that join into a "necklace" or long chain protein molecule. The order of the amino acids makes the protein fold into a certain shape. Most proteins are enzymes, catalyzing chemical reactions. Each different protein controls a different reaction. In other words, the proteins made from the DNA genetic code control all the chemical reactions in the cell that make the cell what it is. The DNA of the parents is in the sperm and egg, so the baby gets half the DNA from each parent. Sections of DNA that code for a particular protein are called genes. So you might have the genes for blue eyes or black hair. Other animals and plants have genes for legs or leaves. Human cells have about 20,000 genes. Environmental factors do play a role in how the genes are "expressed" or used to make proteins, but the code is passed intact from parent to offspring. Hope this helps. Find lots more with Google.

specific nucleotide sequences make up codons, and specific codon sequences code for a particular protein. the lack or presence of a certain protein in an organism determines the appearance and function of an organism's tissues.

Well, if evolution is correct, then we started out as a single cell. The cell creation is unkown. The DNA has instructions to build protiens those protiens form tissue. And if evolution has it right, then we have trial and error and adaption. So like, if you had a prehistorical rodent that couldn't defend itself it would eventually become nocturnal to avoid predators. At night it must learn to see better so it adapted. Why it adapted that way was for the most efficent structure it could make for its enviornment. It wouldn't make sense if the rodent had 5 legs and the 5th on its back.... over time the leg would get smaller and smaller not used and eventually vanish. This is an excellent question! That is the best I could explain how I see it.