Deoxyribonucleic acid

1. Deoxyribonucleic acid Molecular Genetics

4. Deoxyribonucleic Acid I. Introduction Deoxyribonucleic Acid (DNA), is the genetic material of all cellular organisms and most viruses. .

5. DNA carries the genetic information needed to direct protein synthesis and is the only known molecule capable of making a copy of itself (replication).

6. Protein synthesis is the assembly of amino acids into the proteins needed by the cell or virus for its activities and development

7. Replication is the process by which DNA copies itself for each descendant cell or virus, passing on the information needed for protein synthesis.

8. In most cellular organisms, DNA is organized on chromosomes located in the nucleus of the cell.

10. II. Structure A molecule of DNA consists of two chains, strands composed of a large number of chemical compounds, called nucleotides, linked together to form a chain.

11. These chains are arranged like a ladder that has been twisted into the shape of a winding staircase, called a double helix. Each nucleotide consists of three units: a sugar molecule called deoxyribose, a phosphate group, and one of four different nitrogen-containing compounds called bases.

23. The four bases are: adenine (A), thymine (T), guanine (G), cytosine (C). The deoxyribose molecule occupies the center position in the nucleotide, flanked by a phosphate group on one side and a base on the other.

24. Adenine

25. Cytosine

26. Guanine

27. Thymine

28. Purines

29. Pyrimidines

30. The phosphate group of each nucleotide is also linked to the deoxyribose of the adjacent nucleotide in the chain. .

32. These linked deoxyribose-phosphate subunits form the parallel side rails of the ladder.

33. The bases face inward toward each other, forming the rungs of the ladder

36. The nucleotides in one DNA strand have a specific association with the corresponding nucleotides in the other DNA strand.

37. Because of the chemical affinity of the bases, a. Nucleotides containing adenine are always paired with nucleotides containing thymine, b. Nucleotides containing cytosine are always paired with nucleotides containing guanine.

39. The complementary bases are joined to each other by weak chemical bonds called hydrogen bonds.

41. In 1953 American biochemist James D. Watson and British biophysicist Francis Crick published the first description of the structure of DNA.

42. The Double Helix • The double helix of DNA has these features: • It contains two polynucleotide strands wound around each other.The backbone of each consists of alternating deoxyribose and phosphate groups.

43. The phosphate group bonded to the 5' carbon atom of one deoxyribose is covalently bonded to the 3' carbon of the next.The two strands are "antiparallel"; that is, one strand runs 5′ to 3′ while the other runs 3′ to 5′.

44. Their model proved to be so important for the understanding of protein synthesis, DNA replication, and mutation that they were awarded the 1962 Nobel Prize for physiology or medicine for their work.

49. Protein Synthesis DNA carries the instructions for the production of proteins. A protein is composed of smaller molecules called amino acids, and the structure and function of the protein is determined by the sequence of its amino acids.