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Biology
Knowledge of the nucleotide sequence of a gene provides important information about its structure, function, and evolutionary relationship to other similar genes in the same or different organisms. Thus, the development in the 1970s of relatively simple methods for sequencing DNA has had a great impact on genetics. Two basic methods for DNA sequencing have… read more »
Eukaryotic genes consist of coding and noncoding segments of DNA, called exons and introns, respectively.At first glance it seems to be an unnecessary burden to carry DNA without obvious functions within a gene. However, it has been recognized that this has great evolutionary advantages. When parts of different genes are rearranged on new chromosomal sites… read more »
Gene expression and transcription can be influenced by changes of DNA topology. However, this type of control of gene expression is relatively universal and non specific.Thus, it is more suitable for permanent suppression of transcription, e.g., in genes that are expressed only in certain tissues or are active only during the embroyonic period and later… read more »
Although DNA was discovered in 1869 by Friedrich Miescher as a new, acidic, phosphorus containing substance made up of very large molecules that he named “nuclein”, its biological role was not recognized. In 1889 Richard Altmann introduced the term “nucleic acid”. By 1900 the purine and pyrimidine bases were known. Twenty years later, the two… read more »
Some Types of Chemical Bonds close to 99% of the weight of a living cell is composed of just four elements: carbon (C), hydrogen (H), nitrogen (N), and oxygen (O). Almost 50% of the atoms are hydrogen atoms; about 25% are carbon, and 25% oxygen. Apart from water (about 70% of the weight of the… read more »
Cells are the smallest organized structural units able to maintain an individual, albeit limited, life span while carrying out a wide variety of functions. Cells have evolved on earth during the past 3.5 billion years, presumably orginating from suitable early molecular aggregations. Each cell originates from another living cell as postulatedbyR.Virchowin1855(“omniscellula ecellula”).Thelivingworldconsistsoftwobasic types of cells:… read more »