1. DNA
Structure

2. DNA Structure
DNA consists of two molecules that are arranged into a ladder-like structure called a Double Helix.
A molecule of DNA is made up of millions of tiny subunits called Nucleotides.
Each nucleotide consists of:
Phosphate group
Pentose sugar
Nitrogenous base

3. Nucleotides
Phosphate
Nitrogenous
Base
Pentose
Sugar

4. Nitrogen-Containing Bases

5. Sugars

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

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

8. Example of a Nucleoside

9. Nucleotides in DNA and RNA
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

10. Nucleotides
The phosphate and sugar form the backbone of the DNA molecule, whereas the bases form the “rungs”.
There are four types of nitrogenous bases.

11. Nucleotides A
Adenine T
Thymine C
Cytosine G
Guanine

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

13. 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
base
base
base
base
sugar
sugar P
sugar P
sugar P P

14. DNA Structure
Because of this complementary base pairing, the order of the bases in one strand determines the order of the bases in the other strand.

15. Each base will only bond with one other specific base.
Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)
Form a base pair.
Form a base pair.

16. A C T G G A T C

17. 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

18. Double Helix of DNA

19. 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

20. Identical base sequences5’ 3’
Identical base sequences 5’ 3’ 3’ 5’ 5’ 3’
Figure
Watson/Crick proposed mechanism of DNA replication

21. To crack the genetic code found in DNA we need to look at the sequence of bases.
The bases are arranged in triplets called codons.
A G G - C T C - A A G - T C C - T A G
T C C - G A G - T T C - A G G - A T C

22. A gene is a section of DNA that codes for a protein.
Each unique gene has a unique sequence of bases.
This unique sequence of bases will code for the production of a unique protein.
It is these proteins and combination of proteins that give us a unique phenotype.

23. DNA
Gene
Protein
Trait