After the latency period, the virus genes will be turned on and by the usual process of protein synthesis , will hijack the cell's machinery, making viral RNA and proteins, causing virus particles to be produced.
Sometimes, a virus doesn't hijack the cell machinery as soon as it infects the cell. Retroviruses, which possess RNA as their core genetic material carry with them a special enzyme that uses RNA to make a complementary double-stranded DNA molecule. The enzyme (known as reverse transcriptase), synthesizes DNA from the virus' RNA and that DNA can become incorporated into the host cell's genome located in the nucleus.
In either case, the result of viral infection is that the virus' genetic material gets into the cell cytoplasm, which contains all the necessary enzymes and other materials that are needed for the replication of the virus' genetic material and the synthesis of its proteins.
Bacteria are prokaryotes, which means that they do not contain a cell nucleus. Prokaryotes are composed of single cells, although they often grow in groups where the bacteria adhere to each other. These groups of bacteria are called colonies. The bacterial genome consists of a large circular double-stranded DNA molecule, located in the cell cytoplasm. This large DNA molecule, the bacterial chromosome, contains most of the bacterial genes. In addition to this large DNA molecule, bacteria often have smaller circular DNA molecules called plasmids. These plasmids also contain genes, but unlike the large circular chromosome, they are highly mobile. They can be passed easily from one bacterium to another and in this way, genes are passed between bacteria. Plasmid molecules, once i n the recipient bacterial cell, can become permanently integrated into the large bacterial chromosome.
Each sequence of 3 mRNA bases codes for a particular amino acid. For example, the mRNA sequence AUG codes for an amino acid called methionine. Ribosomes, the "machines" that carry out protein synthesis, attach themselves to the mRNA strand and move down it, reading' the sequence of nucleotides and putting together the appropriate protein as they move. The first set of 3 nucleotides the ribosome will read is always AUG. This is because the AUG sequence serves as a marker, telling the ribosome to "start reading here."
Serotonin is an indolamine monoamine neurotransmitter. The synthetic pathway is analogous to the catecholamines in many ways. An important distinction is that the rate limiting step is the uptake of tryptophan into the neuron. Tryptophan availability is the actual rate limiting factor in the intact animal. Tryptophan crosses the blood brain barrier via an active transport mechanism in competetion with other neutral amino acids such as leucine, lysine, and methionine. The activity of this transport mechanism is facilitated by the presence of insulin and glucose. Another interesting aspect of this system is the fact that tryptophan is one of the few amino acids which is bound in the plasma to any significant degree. The actual binding site is the fatty acid binding site of the albumen. This system allows a multitude of factors to ultimately influence the rate limiting step in serotonin synthesis. For example anything which increases free fatty acids would displace the tryptophan and thus increase the percent free which is able to cross the BBB. An example of such events include any acute stressor which increases glucocorticoid response, exercise, and acute alcohol consumption.
The following is a brief overview of how a gene (a section of the DNA molecule ) serves as a template for the synthesis of a protein . The process can be split into two phases.Transcription occurs first, followed by translation.
What happens is that the protein folds into a 3-D structure where most of the hydrophobic amino acids are pointing into the inside of the structure (and away from the water) and where most of the hydrophilic amino acids are on the surface, pointing out into the water. Therefore, the types of amino acids and the order in which they are located in the chain, will determine how the protein will ultimately fold in water, and therefore what its 3-D structure will be in your body.
Proteins, which are floating around within a cell, or just about anywhere else in your body, are surrounded by an environment which is mostly water. What happens to the long chain of amino acids, some of which are hydrophobic and others hydrophilic?
For example, some side groups are non-polar, while others are polar. Polar and non-polar molecules generally stay away from each other. (Have you ever noticed that cooking oil, when added to water, doesn't mix with it, but stays together in large globs? This is because oil molecules are non-polar and water molecules are polar.) Water molecules are polar, and since non-polar molecules don't like to associate with polar molecules, we often call non-polar molecules hydrophobic (derived from Greek, and meaning "water-fearing"). On the other hand, polar molecules are hydrophilic (derived from Greek, meaning "water-loving"), because they love to interact with water.
All proteins are made up of one or several long molecules called polypeptides. Each polypeptide, in turn, is made up of small molecules attached end to end called amino acids. All of the 20 types of amino acids used by living cells have identical "backbone" structures which serve to attach the amino acids together in long chains. Each type of amino acid also has what is referred to as a side group, which is chemically distinct, depending on the amino acid type. While we need not concern ourselves with the fine points of how the structures of the side groups vary, it is important to note that they can be grouped into several categories.
It is the proteins that are responsible for a cell or organism's characteristics. The way in which proteins are constructed, based on a genetic template, is described in the Protein Synthesis section.
RNA is short for RiboNucleic Acid. Like DNA , RNA molecules are manufactured in the nucleus of the cell . However, unlike DNA, RNA is not restricted to the nucleus. It can migrate out into other parts of the cell. Some RNA, called messenger RNA (mRNA) communicate the genetic message found in the DNA out to the rest of the cell for the purpose of promoting the synthesis of proteins . How a gene sequence in DNA is ultimately translated into its corresponding protein is discussed in the Protein synthesis section.