The Information inDNAEach strand provides a template for the exact copying of anewstrandOrder of bases constitutes theDNAcode11
11 • Each strand provides a template for the exact copying of a new strand • Order of bases constitutes the DNA code The Information in DNA
Copyright The McGraw-Hil Companies,Inc.Permission required forreproductionor displayHH-NHSugarSugarNitrogenSugarphosphatephosphatebasepairBase pairsPPhosphateOSugar phosphateDeoxy ribosebackbonewithcarbonnumberCytosineGuanineMinorThy miregrooveAdenineMajor-Hy drogengroovebondCovalent53bond(b)(c)Sugar12(a)
12 Base pairs Sugar phosphate backbone Minor groov e Major groov e 5′ 3′ 3′ P 5′ Phosphate Deoxy ribose with carbon number Cy tosine Guanine Thy mine Adenine Hy drogen bond Cov alent bond A T G C P 5′ 4′ 1′ 2′ 3′ D 3′ D P 5′ OH Sugar phosphate Nitrogen base pair Sugar phosphate 5′ 3′ P N G N-H N H-N Sugar NH H N A H-N N H H Sugar N-H CH3 T H C (a) (b) (c) N N O O H H H H H N N O O 3′ P 5′ 3′ D OH 5′ 4′ 2′ 1′ Copyright © The McGraw -Hill Companies, Inc. Permission required for reproduction or display. N C G C C
Significanceof DNA Structure1. Maintenance of code during reproduction -Constancy of base pairing guarantees that thecode will be retained2. Providing variety - order of bases responsiblefor unique qualities of each organism13
13 Significance of DNA Structure 1. Maintenance of code during reproduction - Constancy of base pairing guarantees that the code will be retained 2. Providing variety - order of bases responsible for unique qualities of each organism
TheMcGraw-Hill CompaniesConcept Check:InDNA,adenine isthecomplementary baseforandcytosine isthe complement forA.guanine,thymineBuracil,guanineC.thymine, guanineD. thymine, uracil
Concept Check: In DNA, adenine is the complementary base for _, and cytosine is the complement for _. A. guanine, thymine B. uracil, guanine C. thymine, guanine D. thymine, uracil
TheOverallReplicationProcessCopyright The McGraw-Hill Companies, Inc. Permission required for reproduction or dis play5'3'.ReplicationoccursParental helixG:CATonbothstrandsGsimultaneouslyT:AT:AG:CECreatesCGReplicationforkcomplementaryCGA: TstrandsATGCG:CA:TA:TATA:TT:AT:ASemiconservativeCCCGReplicasreplication processT:AT:AA:TA:T3'G:C3'5G:C5NewNewParentalParental
The Overall Replication Process • Replication occurs on both strands simultaneously • Creates complementary strands • Semiconservative replication process Copyright © The McGraw -Hill Companies, Inc. Permission required for reproduction or display. 5′ 3′ G C A T T A T A G C A T T A A T C G G C G C G G A T G C G C A T A T A T A T T A T A T A T A A T A T 3 G C 5′ G C 5′ ′ 3′ C G C G C C Parental helix Replication fork Replicas Parental New New Parental