Nucleic Acids
Nucleic Acids Structures of Nucleic Acids DNA Replication RNA and Transcription
Nucleic acids consist of nucleotides that have a sugar, nitrogen base, and phosphate
Base
PO4 Sugar
2 Nitrogen-Containing Bases
O NH2 H CH3 N N N O N N N H H adenine (A) thymine (T) O NH2 O H N CH3 H CH3 N N N
N NH2 N O N O N H H H
guanine (G) cytosine (C) uracil (U) 3 Sugars
HOCH2 O OH HOCH2 O OH
OH OH OH (no O)
ribose deoxyribose
4 Nucleosides in DNA
Base Sugar Nucleoside Adenine (A) Deoxyribose Adenosine Guanine (G) Deoxyribose Guanosine Cytosine (C) Deoxyribose Cytidine Thymine (T) Deoxyribose Thymidine
5 Nucleosides in RNA
Base Sugar Nucleoside Adenine (A) ribose Adenosine Guanine (G) ribose Guanosine Cytosine (C) ribose Cytidine Uracil (U) ribose Uridine
6 Example of a Nucleotide
NH2
N
O O N O- P O CH 2O O-
OH
deoxycytidine monophosphate (dCMP) 7 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 8 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
base base base base
P P P sugar P sugar sugar sugar nucleotide nucleotide nucleotide nucleotide 9 Nucleic Acid Structure NH2
N CMP O O N O- P O CH 2O O- 3 NH2 OH N 3,5-phosphodiester bond N
O 5 N N
O P O CH2 O AMP O-
10 OH 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
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Complementary Base Pairs
•Two H bonds for A-T •Three H bonds for G-C
12 Double Helix of DNA
13 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- • • • • • • • • • • • • • • • • • • • •
14 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-
15 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
16 DNA Unwinds
G- -C G-C A-T A- -T C-G C- + -G T-A T- -A
17 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
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