1. DNA structure and function

2. Major points
Genetic information flows from DNA to RNA to protein (“central dogma”)
DNA is a double helix of two complementary antiparallel strands
Specific pairing occurs between bases of nucleic acid (DNA and RNA) strands

3. Reading (3)
Chapter 5, pp
Chapter 16, pp

4. DNA structure and function
I. Nucleic acid function
1.Overview
(replication, transcription, translation)
2. Genetic information flow
(DNA -> RNA -> protein)
3. Definition of gene
II. Nucleic acid structure

5. Nucleic acid function overview
DNA
Replication
Transcription
RNA
Catalysis
Translation
Protein

6. Nucleic acid function DNA stores hereditary information (genes)
RNA transmits hereditary information

7. DNA function (genes)
DNA is a polymer that stores and carries genetic information
Information is stored as the sequence of monomer subunits (nucleotides)

8. Definition of gene Genes are the units of heredity
Genes direct RNA and protein syntheses (“Central dogma”)
“One gene encodes one protein”
(with exceptions)

9. DNA-> RNA-> protein
Is this cell eukaryotic or prokaryotic?

10. “Central dogma” RNA can be reverse transcribed to DNA DNA
catalyzed by protein
RNA
RNA has catalytic activity
Protein
Transcription
RNA synthesis using DNA template
Translation
Protein synthesis using RNA template

11. “One gene-one protein”
Genes are the units of heredity
Each gene encodes one protein
However there are exceptions:
-multisubunit proteins
-alternative RNA splicing or protein processing
-regulatory DNA and catalytic RNA

12. DNA structure and function
I. Nucleic acid function
II. Nucleic acid structure
1. Nucleotides
2. Double helix
3. Complementary base-pairing
4. Supercoiling

13. Watson & Crick
DNA
Double helix

14. DNA structure Polymer of nucleotide subunits A, T, G, C
Base-pairing (complementary)
A=T and CG
Double helix (Watson & Crick)
antiparallel
right-handed

15. Nucleotides Monomeric subunits of nucleic acids Composed of:
Phosphate group
Five-carbon sugar: ribose (RNA) or deoxyribose (DNA)
Nitrogenous base

16. Nucleotide structure

17. Double helix Two polynucleotide strands
Antiparallel (sugars: 5´ to 3´ and 3´ to 5´)
Right-handed (B-form)
Held together by:
Pairing between bases (H-bonds)
Stacking interactions

18. Double helix structure

19. Complementary base-pairing
A binds T (or U)
T (or U) binds A
G binds C
C binds G
Which is stronger?

20. Levels of DNA structure
Primary structure: sequence of nucleotides
Secondary structure: path of strands
double helix
Tertiary structure: path helix takes in space
supercoiling

21. Telephone cord
relaxed
supercoiled

22. DNA topoisomerases Enzymes that alter DNA topology
DNA gyrase is the only topoisomerase that introduces negative supercoiling

23. Bio 103 home