DNA and RNA

DNA to protein translation process   - This one-way flow of information from DNA to protein is called the central dogma of molecular biology. Information stored in DNA is copied to RNA (transcription), which is used to assemble proteins (translation). Each DNA strand is composed of sub-units called nucleotides or, “bases” for short.  There are four types of nucleotides – adenine, A; thymine, T; guanine, G and cytosine, C. An A always pairs with T, and G with C. Thus the two strands of DNA are complementary to each other. Nucleotides are arranged in a specific order on DNA – this is called the sequence of DNA.  This sequence is further sectioned into genes – a short segment of DNA that is made into one polypeptide (protein) chain. Cells convert DNA to protein in a two-step process. Transcription: DNA to RNA Transcription occurs in the nucleus. Transcription in the process by which RNA is assembled from a DNA template. To transcribe a gene, th...

Trisomy 13 or Patau Syndrome  is the most severe viable trisomy caused by an additional copy of chromosome 13 that usually causes a host of developmental problems and physical deformities in a newborn. Patau syndrome is generally recognized at birth by the presence of structural birth defects and poor neurologic performance. Additional structural anomalies are common, particularly facial anomalies (midline clefts, hypotelorism, microphthalmia, and anophthalmia) arising from structural anomalies of the brain, frequently microcephaly and holoprosencephaly. Other associated anomalies include cardiac, renal, and intestinal (diaphragmatic hernia) anomalies. Characteristic features include low set ears, post-axial polydactyly, flexion contractures, rocker bottom feet, scalp defects, and haemangiomas. What is the cause of Patau Syndrome ? The exact incidence of Patau syndrome is not known, although it appears to affect females more than males, most likely because ...

What is Complementary Bases in DNA ? -  DNA is made up of two chains of molecules called nucleotides; thing of it as two bead necklaces, each bead being a nucleotide. Complementary base pairing ensures that the daughter DNA molecule obtained during replication is exactly like that of the original strand. DNA replication is semiconservative and at such, complementary base pairing ensure that if adeinine is found on one strand, thymine is found on the other complementary base pairing also help to hold the double helix together by the formation of hydrogen bond. The two chains (or strands) are joined by each bead (nucleotide) so that it looks like a ladder (a helix). The bonds between the nucleotides on the two strands are hydrogen bonds, and these are formed between a special part of the nucleotide called a base (or nitrogenous base). DNA double helix is formed Video Scheme of unusual pairing of complementary bases in DNA : Besides the normal pairing of Dna bases,...

Synthesis Direction of DNA -  When DNA is synthesized, the free 3´ hydroxyl (OH) group from the growing strand of DNA attacks the phosphate on the next base to be added. When a cell divides, it passes on genetic information by producing copies of its DNA. Chemists have also learned to copy DNA. In the journal Angewandte Chemie, a German team has now introduced a new copying technique that uses a single strand of DNA as the “master copy”, like a cell, but does not require enzymes. Pyrophosphate is released and the new base forms a phosphodiester bond with the growing strand of DNA. The free 3´ hydroxyl group is then freed to attack the next base to be added. Within a cell, the DNA double strand is separated in segments during the copying process. One of the single strands serves as the “master copy” or template. Polymerase enzymes snap together the corresponding nucleotides stepwise to form the new complementary strand, beginning with a “starting segment” know...