{"id":282,"date":"2024-03-23T09:40:16","date_gmt":"2024-03-23T09:40:16","guid":{"rendered":"https:\/\/pressbooks.justwrite.in\/interactive-biology-secondary\/?post_type=chapter&p=282"},"modified":"2024-11-02T18:42:29","modified_gmt":"2024-11-02T18:42:29","slug":"5-6-molecular-basis-of-inheritance","status":"publish","type":"chapter","link":"https:\/\/pressbooks.justwrite.in\/interactive-biology-secondary\/chapter\/5-6-molecular-basis-of-inheritance\/","title":{"raw":"5.6 Molecular basis of inheritance","rendered":"5.6 Molecular basis of inheritance"},"content":{"raw":"

DNA<\/h1>\r\nThe genetic (hereditary) material for all living things is composed of DNA (deoxyribonucleic acid). It is the blue print of an organism. The DNA stores the coded information that control the biological function of cells.<\/span>\r\n\r\n\u00a0 The genetic material transmits this hereditary information in a stable form for the cell and organism through a molecular process called <\/span>\u00a0<\/span>replication<\/strong>\u00a0of DNA. <\/span>\r\n\r\nThe replication process ensures high accuracy in copying the genetic information so that all progeny cells receive the same information.\u00a0<\/span>\r\n

Chemical\u00a0Structure of DNA\u00a0Subunits<\/h2>\r\nDNA is a polymer made of nucleotide subunits.\r\n\r\nA\u00a0<\/span>nucleotide<\/strong>\u00a0<\/span>consists of 3 chemical groups; a sugar, a phosphate and a nitrogenous base . In the case of DNA, the sugar is deoxyribose and in Ribonucleic acid (RNA), the sugar is ribose\r\n\r\nDNA contains\u00a0 four types of nitrogenous bases namely Adenine (A) and guanine (G) , which are double-ringed purines, and cytosine (C) and thymine (T) , which are smaller, single-ringed pyrimidines. The nucleotide is named according to the nitrogenous base it contains.<\/span>\r\n\r\n\r\n

\"DNA Nucleotide\"<\/a>\u00a0by\u00a0<\/span>Charles Molnar and Jane Gair\u00a0<\/span><\/a><\/a><\/a>is licensed under\u00a0<\/span>CC BY 4.0<\/a><\/p>\r\n\r\n

\"Purines and Pyrimidines\"<\/a>\u00a0by\u00a0<\/span>Charles Molnar and Jane Gair\u00a0<\/span><\/a><\/a><\/a>is licensed under\u00a0<\/span>CC BY 4.0<\/a><\/p>\r\n DNA molecule is actually composed of two single strands held together along their length with hydrogen bonds between the bases.<\/span>\r\n\r\nEach of the DNA strand\u00a0 is a long polymer of\u00a0 nucleotides is formed by the nucleotide polymerisation where a phosphate group of one nucleotide bonds covalently with the sugar molecule of the next nucleotide, and so on, . <\/span>\r\n\r\nThe sugar\u2013phosphate groups line up in a \u201cbackbone\u201d for each single strand of DNA, and the nucleotide bases stick out from this backbone. <\/span>\r\n\r\nThe carbon atoms of the five-carbon ,deoxy ribose sugar are numbered clockwise from the oxygen as 1\u2032, 2\u2032, 3\u2032, 4\u2032, and 5\u2032 (1\u2032 is read as \u201cone prime\u201d).<\/span>\r\n\r\n The phosphate group is attached to the 5\u2032 carbon of one nucleotide makes a nucleophilic attack on the OH group at 3\u2032 carbon of the next nucleotide and forms a phospho di ester bond , linking the nucleotides together.<\/span>\r\n\r\nThe two strands\u00a0 strands of DNA are twisted around each other to form a right-handed\u00a0 double helix.<\/span>\r\n\r\n Base-pairing takes place between a purine and pyrimidine: namely,\u00a0<\/span>A pairs with T, and G pairs with C<\/strong>.<\/span>\r\n\r\nThis is the basis for Chargaff\u2019s rule i.e.,<\/strong> due to the complementarity of the bases ,\u00a0there is as much adenine as thymine in a DNA molecule and as much guanine as cytosine. <\/span>\r\n\r\nAdenine and thymine are connected by two hydrogen bonds, and cytosine and guanine are connected by three hydrogen bonds. <\/span>\r\n\r\nThe two strands of DNA are anti-parallel in nature; that is, one strand will have the 3\u2032 carbon of the sugar in the \u201cupward\u201d position, whereas the other strand will have the 5\u2032 carbon in the upward position.<\/span>\r\n\r\n \r\n\r\n\r\n

\"DNA\"<\/a>\u00a0by\u00a0<\/span>Charles Molnar and Jane Gair\u00a0<\/span><\/a><\/a><\/a>is licensed under\u00a0<\/span>CC BY 4.0<\/a><\/p>\r\n\r\n

The Structure of RNA<\/h1>\r\n

There is a second polymer of nucleotides in the cell ,\u00a0 called ribonucleic acid, or RNA.<\/p>\r\nEach of the nucleotides in RNA is made up of\r\n