Hereditary information

Deoxyribonucleic acid (DNA, Fig. 3-13) is the genetic material of all organisms, including plants, animals, and microorganisms. (Some viruses lack DNA, but use RNA (ribonucleic acid) in its place.) DNA carries all the hereditary information of the organism and is therefore replicated and passed from parent to offspring. RNA is formed on DNA in the nucleus of the... 

DNA bases carry the hereditary information and therefore must be protected. 

Two nucleic acids, deoxyribonucleic acid (8.1, DNA) and ribonucleic acid (8.2, RNA), constitute, respectively, the molecules that store hereditary information and those that transcribe and translate such hereditary information, thus enabling the directed synthesis of varied but specific proteins throughout the cell and the entire organism. These nucleic acids are biopolymers, composed of monomeric building units called nucleotides (figure 8.2). Just as proteins can be hydrolyzed to amino acids and polysaccharides can be hydrolyzed to monosaccharides, nucleic acids can be hydrolyzed to nucleotides. 

The four bases whose sequence determines the hereditary information in ribonucleic acid (RNA), the naturally occurring polynucleotide, are adenine, cytosine, guanine, and uracil. These structures are as shown in Figure A. 

Nucleic acids are organic polymers that carry hereditary information, which in turn directs the synthesis of all the proteins in the body. There are two nucleic acids—deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). 

DNA has the unusual ability to make exact copies of itself, a process called replication. It is this ability that allows the hereditary information to be passed from one generation to the next. 

The hereditary information, or genetic code, resides in the order of the nucleotides in DNA. This information is copied from the DNA in the cell nucleus into molecules of a special RNA, which passes out of the nucleus to the sites of protein synthesis. Here, the code copied into the RNA determines which proteins are synthesized. These, in turn, determine the structure and functions of the cells and of the organism as a whole. 

Deoxyribonucleic acid (DNA) A polymer of nucleotides that contains the hereditary information of the organism. 

Genetic code The hereditary information passed from generation to generation and found in the order of nitrogen bases in DNA the code controls protein synthesis in the organism. 

Nucleic acids DNA and RNA DNA carries the hereditary information, while RNA carries this information from the cell nucleus to the sites of protein synthesis. 

Deoxyribonucleic acid (DNA) The constituent of chromosomes which stores die hereditary information of an organism in the form of a sequence of nitrogenous bases. Much of this information relates to the synthesis of proteins, other agents. 

Chromosome. A threadlike structure, visible in the cell nucleus during metaphase, that carries the hereditary information. 

The cloning of a gene is the central operation of recombinant DNA technology. Gene is the basic unit of hereditary information located on a chromosome of the cell. Chromosomes are threadlike structures found in the nucleus, which are comprised primarily of DNA. The... 

In 1989, Sidney Altman and Thomas Cech were awarded the Nobel Prize in chemistry for a discovery that changed not only the field of biocatalysis, but also our perception of the molecular basis of life on Earth [118]. They showed that RNA, which until then was considered an innocent carrier of hereditary information, can actually catalyze reactions [119,120]. Two different RNA molecules were shown to catalyze site-specificphosphodiesterbondcleavage,withrate enhancements ofseveral orders of magnitude. This discovery of nonprotein biocatalysts came as a complete surprise, and laid open many questions and opportunities [121,122]. 

Nucleus The nucleus of an atom is the positively charged portion of the atom that contains protons and neutrons. Negatively charged electrons are found in the space around the nucleus. The nucleus of a cell, which is surrounded by a membrane, contains the chromosomes with their DNA and hereditary information. 

The complete set of genes that contain all the hereditary information of a particular species is called a genome. The Human Genome Project, initiated in 1990, has identified all the genes that occur in humans and also the sequence of bases in these genes. 

Chromosomes In bacteria, a circular strand of DNA that contains the hereditary information. In eukaryotic cells (higher organisms such as plants), chromosomes consists of linear strands of DNA comprised of tens of thousands of genes. They are found in the nucleus of every cell. 

That view of the origin of life has commonly been called metabolism first the absence of a genetic polymer has been equated with the lack of any mechanism for heredity. As we have seen, replicator theories center on the spontaneous formation of large, information-bearing organic polymers endowed with the ability to copy themselves. The hereditary information carried in the sequence of such a polymer is called a genome. 

In the words of Lancet and colleagues, a fundamentally different approach has envisaged primordial selfreplication as the collective property of ensembles of relatively simple molecules, interconnected by networks of mutually catalytic interactions. 38 The hereditary information in this case would be represented by the identity and concentration of its components. The term compositional genome has been used to describe this system, in which genetic information is not stored in a list, as in DNA, but is represented by the presence or absence of organic components.39,40 As an analogy, consider DNA to be the equivalent of a class list that records the full possible enrollment in a course. The information in a compositional genome would be represented by the presence of students who have turned up on a particular day. 

---