The document discusses the structures and components of nucleic acids DNA and RNA. It explains that nucleic acids are made up of nucleotides, which contain a sugar, phosphate, and one of four nitrogenous bases. The sugars in DNA are deoxyribose and in RNA are ribose. The four bases are adenine, guanine, cytosine, and either thymine in DNA or uracil in RNA. Nucleotides are linked by phosphodiester bonds to form long chains. DNA has a double helix structure with the bases on one strand pairing with their complement on the other strand through hydrogen bonds between A-T and G-C base pairs. DNA replication involves the unwinding of the DNA double helix, and

1. Nucleic Acids Nucleic Acids Structures of Nucleic Acids DNA Replication RNA and Transcription

2. Nucleotides Nucleic acids consist of nucleotides that have a sugar, nitrogen base, and phosphate nucleoside Sugar Base PO 4

3. Nitrogen-Containing Bases

4. Sugars

5. Nucleosides in DNA Base Sugar Nucleoside Adenine (A) Deoxyribose Adenosine Guanine (G) Deoxyribose Guanosine Cytosine (C) Deoxyribose Cytidine Thymine (T) Deoxyribose Thymidine

6. Nucleosides in RNA Base Sugar Nucleoside Adenine (A) ribose Adenosine Guanine (G) ribose Guanosine Cytosine (C) ribose Cytidine Uracil (U) ribose Uridine

7. Example of a Nucleotide

8. Nucleotides in DNA and RNA DNA dAMP Deoxyadenosine monophosphate dGMP Deoxyguanosine monophosphate dCMP Deoxycytidine monophosphate dTMP Deoxythymidine monophosphate RNA AMP adenosine monophosphate GMP guanosine monophosphate CMP cytidine monophosphate UMP uridine monophosphate

9. Structure of Nucleic Acids Polymers of four nucleotides Linked by alternating sugar-phosphate bonds RNA: ribose and A, G, C, U DNA: deoxyribose and A,G,C,T nucleotide nucleotide nucleotide nucleotide P sugar base P sugar base P sugar base P sugar base

10. Nucleic Acid Structure 3,5-phosphodiester bond 3 5

11. Double Helix of DNA DNA contains two strands of nucleotides H bonds hold the two strands in a double-helix structure A helix structure is like a spiral stair case Bases are always paired as A–T and G-C Thus the bases along one strand complement the bases along the other

12. Complementary Base Pairs Two H bonds for A-T Three H bonds for G-C

13. Double Helix of DNA

14. Learning Check NA1 Write the complementary base sequence for the matching strand in the following DNA section: -A-G-T-C-C-A-A-T-G-C- • • • • • • • • • • • • • • • • • • • •

15. Solution NA1 Write the complementary base sequence for the matching strand in the following DNA section: -A-G-T-C-C-A-A-T-G-C- • • • • • • • • • • • • • • • • • • • • -T-C-A-G-G-T-T-A-C-G-

16. DNA Replication DNA in the chromosomes replicates itself every cell division Maintains correct genetic information Two strands of DNA unwind Each strand acts like a template New bases pair with their complementary base Two double helixes form that are copies of original DNA

17. DNA Unwinds G- -C A- -T C- + -G T- -A G-C A-T C-G T-A

18. DNA Copied with Base Pairs Two copies of original DNA strand G-C G-C A-T A-T C-G + C-G T-A G-A