Protein genetic blueprint

Figure 10.4. Translation of the genetic blueprint into proteins. Alternative splicing leads to isoforms. After translation proteins are often modified to become functional.

Proteins are a diverse family of large molecules composed of 20 amino acid building blocks. They are an integral part of our diet. Our genetic blueprint codes for proteins produced inside our cells that promote the chemical reactions of life, protect us from infection, act as communication devices, facilitate transport of molecules and ions, mediate movement, and provide structure for our cells and bodies. 

Simplicity argues that the genetic blueprint specifying amino acid sequences in proteins should consist of consecutive, nonoverlapping triplets. This assumption turned out to be correct, as is illustrated by the DNA sequence for a gene shown in Fig. 5-5. In addition to the codons that determine the sequence of amino acids in the protein, there are stop codons that tell the ribosomal machinery when to terminate the polypeptide chain. One methionine codon serves as an initiation codon that marks the beginning of a polypeptide sequence. One of the valine codons sometimes functions in the same way. 

DNA contains the full genetic blueprint for an organism. Every enzyme, receptor, and structural protein is encoded by DNA in subsections called genes. Collectively, all the genes of an organism comprise its full genome. For humans, the full genome consists of over 3 billion nucleotide pairs.2... 

In bacterial cells, nucleic acids are found in the form of deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). DNA carries the genetic blueprint for the cell and RNA acts as an intermediary molecule to convert the blueprint into proteins [8]. RNA has three forms namely, ribosomal, messenger and transfer RNAs. All the three types of RNA are essential for protein synthesis. Ribosomal RNA is the most abundant macromolecule, next to proteins, in an actively growing prokaryotic cell. It is a major component of the ribosome, the cellular machinery used to synthesize new proteins. There are three ribosomal RNA molecules in prokaryotes namely 5S (ca. 120 nucleotides), 16S (1500 nucleotides), and 23S (2900 nucleotides). 

The number of different protein species in plasma is in the hundreds of thousands with some estimates as high as 500 000 all of these are ultimately derived from the genetic blueprint carried in the DNA of all cells in the individual organism, but in humans the number of identifiable genes is only 30000. One important... 

FUNCTIONS. DNA is the component of the chromosomes that carries the blueprint for a species—the heritable characteristics of each cell in the body and its descendants. It functions in the egg and sperm cells to pass the blueprint along from parent to offspring. Messages are relayed from DNA in the nucleus of cells to the cytoplasm by RNA, where upon the sequences of amino acids in protein synthesis are dictated by the order of the purine and pyrimidine bases transcribed from the DNA. Each cell of the body contains a full genetic blueprint, but only small parts of the genetic message are normally transcribed by RNA for cells to fulfill their role in whatever tissue they are located. 

Whereas DNA has a single role as the storehouse of genetic information, RNA plays many roles in the operation of a cell. There are several different types of RNA, each having its own function. The principal job of RNA is to provide the information needed to synthesize proteins. Protein synthesis requires several steps, each assisted by RNA. One type of RNA copies the genetic information from DNA and carries this blueprint out of the nucleus and into the cytoplasm, where construction of the protein takes place. The protein is assembled on the surface of a ribosome, a cell component that contains a second type of RNA. The protein is consfructed by sequential addition of amino acids in the order specified by the DNA. The individual amino acids are carried to the growing protein chain by yet a third type of RNA. The details of protein synthesis are well understood, but the process is much too complex to be described in an introductoiy course in chemistry. 

The presence of RNA in the cytoplasm had been linked to protein synthesis by experiments done in the early 1940s. After the discovery of the double helix, the concept followed quickly that DNA was the master "blueprint" from which secondary blueprints or transcripts of RNA could be copied. The RNA copies, later identified as messenger RNA (mRNA), provided the genetic information for specifying protein sequence. The flow of information from DNA to RNA to proteins could be symbolized as in Eq. 26-1. 

DNA (deoxyribonucleic acid) The basic genetic material found in all living cells (and some viruses), providing the blueprint (i.e. genes) for construction of proteins. DNA is composed of sugars, phosphates, and bases arranged in a double helix, a double stranded, chain-like molecules composed of nucleotide base pairs. 

DNA serves as a blueprint for the individual, controlling, among other aspects, the production of highly specific proteins. In sexual reproduction, the DNA of the offspring is derived from the DNA of both parents, and so serves as the material basis of inheritance and of evolution. Cloning experiments, from Dolly the sheep onward genetically modified crops the possible treatment of inherited diseases—in these and other ways, an understanding of the chemical basis of reproduction and in-... 

A non-dividing nucleus (in a state) resting, is actually making the molecules which allow the rest of the cell to function. One of the most important events taking place in the nucleus is transcription, which is the transfer of the instructions on the DNA to the RNA. DNA is a stable store of genetic information, which must be transcribed (via RNA molecules) to construct the proteins coded in its blueprint. 

Living things use nucleic acids to carry genetic information based on the identity of the amine base present. This information is used to determine the amino acid sequence of every protein in the organism and it provides a blueprint for how the organism is made. 

---