In prior epochs, it was appropriate to explain talents, illnesses, vices, virtue and other heredity by statement: “it is in someone's blood”. However, with the lapse of time, scientists began questioning the blood theory of inheritance. It was a long way to the realization that DNA transmits heredity. By the end of the 19th century, the theory of characteristics inheritance through blood was challenged and finally discarded. In its stead, scientists began an exploration of nucleic acid molecules, which are arranged into biological units called genes, and the genetic theory of transmitting characteristics inheritance has become one of the basal fundamentals of modern science (Watson, 2003).
The functions of DNA are essential for characteristic inheritance, encoding for proteins and the genetic blueprint of living organisms. Two functions of DNA are the regulations for an organism's biological development and reproduction. DNA contains in the coding for proteins, which are compound molecules that necessary for vital functions of an organism. Ciphered information of DNA is transcribed by a messenger molecule that translated it into the understandable language for the body. Transmitters are amino acids, which are the building compounds of proteins at the same time. It transmits in what way the amino acids have to produce a specific protein (Watson, 2003).
DNA replication is indispensable for a huge amount of functions, beginning from reproduction to cells and tissues growth, as well as growth of body systems. DNA consists of phosphate, a sugar and four bases, which are part of a nucleotide. In a reproductive sense, combination of the egg and sperm DNA produces the first cell with completed genetic code for developing new life; in this cell half of chromosomes with DNA is originated by father and the second half is originated by mother (Dale, 2012).
Structure of a Nucleotide
Nucleotide comprises a pentose, four nitrogenous bases, and one or more phosphate groups. Two kinds of a class of simple sugars (pentose), which molecules contain five carbon atoms are identified: Deoxyribose, which contains a hydrogen atom, and Ribose, which contains a hydroxyl group. The monomers of DNA (deoxyribonucleic acids) are nucleotides that contain deoxyribose. The ribonucleotides, nucleotides contain ribose, are the monomers of RNA (ribonucleic acids). A ring structure that contains nitrogen is named a base. Four bases of DNA are two purines, which are adenine and guanine, and two pyrimidines, which are thymine and cytosine. Four bases of RNA are two purines, which are guanine and adenine, and the pyrimidine cytosine, but in thymine stead, there is the pyrimidine uracil (Dale, 2012).
The bases always pairs as following: A always pairs with T, and C always pairs with G. In other words, the purine adenine is in pair with the pyrimidine thymine, and the pyrimidine cytosine is in pair with the purine guanine. The explanation to this phenomenon is following: two purines cannot be arranged within the helix, as well as two pyrimidines cannot approach each other in order to form hydrogen bonds owing the extra space between them. Such relationships are also named as the rules of Watson-Crick base pairing. According to these rules, the amount of adenine always equalizes with the amount of thymine in the DNA of an organism (Chargaff’s rule). Similarly, the amount of guanine always equalizes with the amount of cytosine (Dale, 2012).
Process of Replication, Including Enzyme Function
The replication process of DNA commences when particular enzymes break up, or, other words, they “unzip” the DNA double helix. After the two strands are separated, the purine and pyrimidine bases on each strand became easy to access. The available bases started attracting their complementary bases. The enzyme DNA polymerase connects the nucleotide units to one another, creating a long chain of nucleotides. Therefore, the chain of DNA organizes the synthesis of a daughter chain of DNA due to complementary base pairing. The maternal chain then connects with the daughter chain to re-form a double helix (Fitzgerald-Hayes, 2010).
RNA has the similar structure as DNA; therefore, made of 4 building bases, which are the ribonucleotides. The thymine is altered in a way that a methyl group is absent; thus uracil takes thymine stead in base pairing. The ribose forms in its complete hydroxylated form. The two features, which are the uracil instead of thymine, and the 2'-OH in the ribose creates the two main chemical distinctions between RNA and DNA. However, RNA also various from DNA as it does not create an analogous double helical structure (Dale, 2012).
Process of Transcription
DNA transcription is a biological procedure that includes the transcribing of genetic data from DNA to RNA. The transcribed DNA message is utilized to provide proteins. DNA is located within the nucleus of organism’s cells, and supervises the cellular processes by coding for the reproduction of enzymes and proteins. The DNA data is not immediately encoded into proteins; it should initially be copied into RNA. Such process provides that DNA data does not become corrupted (Fitzgerald-Hayes, 2010).
In the translation process, the particular cells called ribosomes play the leading role. The ribosomes work as translators, and they translate the specific messenger's code into the appropriate protein format or a string of amino acids that create the building units of the protein. Each amino acid is created by combining the three bases on the RNA (Fitzgerald-Hayes, 2010).
A Codon and an Anticodon
A codon is located in the messenger of RNA (mRNA), whereas the anticodon is the complete opposite of a codon. Therefore, if the codon is G C A, the anticodon should be the opposite, and that means C G U. The codon and anticodon act together to facilitate the creating of protein chains. The codon is something kind of code of the necessary protein. The transfer RNA (tRNA) gathers free nucleotides of RNA and moves them to the Ribosome to form an anticodon which provides a specific protein to the ribosome. There is an anticodon with complementary bases to a codon on the messenger RNA chain for each transfer RNA (Fitzgerald-Hayes, 2010).
Usage of DNA Technology
DNA technology has changed the modern science. DNA is inherited from ancestors to descendants, and holds keys to the some mysteries of disease, aging and human evolution. The discoveries of last two decades in the DNA technology include recombinant DNA technology, cloning, PCR, gene therapy, DNA fingerprinting, DNA profiling and DNA microarray; these discoveries are indispensable for development of forensic science, medicine, national security and environmental sciences (Dale, 2012).
Deoxyribonucleic acid profile is unique, so it is a crucial forensic tool. Two well-known methods are applied to determine the DNA profile: RFLP (Restriction fragment length polymorphism) and STR (Short tandem repeat profiling) (Dale, 2012).
The advances of huge progress result in databases of species genome sequences, microarray profiles of various cell lines expression, unique nucleotide polymorphisms or various mutations. New discoveries gain vast usage in the pharmaceutical industry. The newest discoveries are the genome sequencing and the DNA chip technology. The modern nanostructures have three dimensions, which can retain and release drugs, as well as control protein-folding. Gene therapy can use the corrective enzyme to the particular defective gene for identifying and correcting it. The DNA extracted from archaeological samples is used to track DNA evolution of species and migratory patterns (Watson, 2003).
Like the thread of the three fatal sisters from Greek mythology, DNA is the necessity of continuing the human life. It contains essential data that convey to descendants from ancestors. If DNA changes, at least, slightly, serious and, often, unfavorable aftereffects will result. The cell will die if DNA is destroyed, for example, by cancer. DNA modification of organism’s cells creates various versions of the species characteristics. In the long course of time, natural selection develops on these various versions to evolve and change the species (Dale, 2012).
The DNA often becomes crucial evidence if it is found at a crime scene for convicting or acquitting a criminal suspect. Eventually, the DNA that extracted from the single cell provides the possibility for cloning an animal, a plant, or even a human being. DNA is so essential that the United States government grants every year huge amounts of money to resolve the sequence of DNA in the human genome in order to apprehend and find cures for every genetic disease (Hayes, 2010).