Basics of DNA & RNA (Nucleic acid)

Basics of DNA & RNA (Nucleic acid)

1. DNA Sequencing

2. Two types of nucleic acid are found Deoxyribonucleic acid (DNA) Ribonucleic acid (RNA)

3. DNA as genetic material: The circumstantial evidence Present in all cells and virtually restricted to the nucleus The amount of DNA in somatic cells (body cells) of any given species is constant (like the number of chromosomes) The DNA content of gametes (sex cells) is half that of somatic cells. In cases of polyploidy (multiple sets of chromosomes) the DNA content increases by a proportional factor

4. Nucleotides Nucleotides are the subunits of DNA and RNA. They participate in numerous biological processes, convey energy, are part of essential coenzymes, and regulate numerous metabolic functions.

5. Three integral part of nucleotides a phosphate group, a sugar (pentose), and a purine or pyrimidine base (nitrogenous base). Nucleoside The molecule without the phosphate group is called a nucleoside

6. Nucleosides vs nucleotides A nucleoside is a compound of a sugar residue (ribose or deoxyribose) and a nucleotide base. The bond is between the C atom in position 1 of the sugar and an N atom of the base (N-glycosidic bond). A nucleotide is a compound of a five-C-atom sugar residue (ribose or deoxyribose) attached to a nucleotide base (pyrimidine or purine base) and a phosphate group. The nucleosides of the various bases are grouped as ribonucleosides or deoxyribonucleosides, e.g., adenosine or deoxyadenosine, guanosine or deoxyguanosine, uridine (occurs only as a ribonucleoside), cytidine or deoxycy tidine. Thymidine occurs only as a deoxynucleoside.

7. NUCLEOTIDE STRUCTURE PHOSPATE SUGAR Ribose or Deoxyribose NUCLEOTIDE BASE PURINES PYRIMIDINES Adenine (A) Guanine(G) Cytocine (C) Thymine (T) Uracil (U) © 2007 Paul Billiet ODWS

8. The Structure of Nucleotide

9. A. Phosphate groups Phosphate groups occur in nucleic acids and nucleotides as monophosphates (one P atom), diphosphates (2), or triphosphates (3).

10. Phosphate group It consists of a phosphorus atom bonded to four oxygen atoms. Phosphate groups are found in every nucleotide and frequently carry a negative charge, which makes DNA acidic. The phosphate is always bonded to the 5-carbon atom of the sugar in a nucleotide

11. SUGAR The carbohydrate residues in nucleotides are usually derived from either ribose (in ribonucleic acid, RNA) or deoxyribose (in deoxy ribo nucleic acid, DNA) (ribonucleoside or deoxyribonucleoside).

12. Ribose is a pentose C 1 C 5 C 4 C 3 C 2 O © 2007 Paul Billiet ODWS

13. Ribose vs Deoxyribose

14. Ribose vs Deoxyribose This minor chemical difference is recognized by all the cellular enzymes that interact with DNA or RNA, thus yielding specific functions for each nucleic acid. Further, the additional oxygen atom in the RNA nucleotide makes it more reactive and less chemically stable than DNA. For this reason, DNA is better suited to serve as the long-term repository of genetic information.

15. THE SUGAR-PHOSPHATE BACKBONE The nucleotides are all orientated in the same direction The phosphate group joins the 3 rd Carbon of one sugar to the 5 th Carbon of the next in line. P P P P P P © 2007 Paul Billiet ODWS

16. Nitrogenous Bases Nucleotide bases of pyrimidine Cytosine (C), thymine (T), and uracil (U) are the three pyrimidine nucleotide bases. They differ from each other in their side chains (—NH2 on C4 of cytosine,—CH3 on C5 in thymine,and O on C4 in uracil). In addition, cyotsine has a double bond between N3 and C4. Nucleotide bases of purine Adenine (A) and guanine (G) are the two nucleotide bases of purine. They differ in their side chains and in having a double bond between N1 and C6 (present in adenine, absent in guanine). Note; Free pyrimidines and purines are weakly basic compounds and are thus called base

17. Nitrogenous base

18. Phosphodiester Linkage

19. Glycosidic Bond The nitrogen atom in position 9 of a purine or in position 1 of a pyrimidine is bound to the carbon in position 1 of the sugar (N-glycosidic bond). The glycosyl bond is formed by removal of the elements of water (a hydroxyl group from the pentose and hydrogen from the base), as in O-glycosidic bond formation

20. Four types of nucleotide