3. DNA
• DNA isamoleculecalled deoxyriboucleic
acid.
• It isthehereditary material in humansand
almost all other organisms.
• All organismshaveblueprintsthat contain
information that will determinetheir physical
and chemical characteristics. Thisblueprint is
DNA.
4. • DNA isoften referred to ascodeof life
becauseit containsall theinformation needed
to form and control thephysical makeup and
chemical processesof an organism.
5. Where can you find DNA
• DNA is mainly found in the nucleus of
eukaryotic cells and in the nucleoid region
of prokaryotic cells.
6.
7. • DNA isavery largemoleculemadeup of a
long chain of sub-units.
• Thesub-unitsarecalled nucleotides
Each nucleotideismadeup of
asugar called deoxyribose
aphosphategroup -PO4 and
an organic base
8. The nitrogenous bases are:
The bases
Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G
)
11. • In fact, theDNA usually consistsof a
doublestrand of nucleotides.
• Thesugar-phosphatechainsareon the
outsideand thestrandsareheld together
by chemical bondsbetween thebases
13. The bases always pairup in the
same way
Adenineformsabond with Thymine
Adenine Thymine
and Cytosinebondswith Guanine
Cytosine Guanine
14. Nitrogen Bases are classified
into two groups:
1. Purines- Thetwo-carbon nitrogen ring bases.
(adenineand guanine)
2. Pyrimidines- one-carbon nitrogen ring bases.
(thymineand cytosine)
18. Remember
• A phosphategroup, sugar moleculeand a
baseform anucleotide.
• A chain of nucleotideform of aDNA
molecule.
19. Question 1
Which of the following are components of
nucleotides?
(a) deoxyribose
(b) amino acids
(c) phosphate
(d) enzymes
(e) organic bases
20. Question 2
Which of the following represent a correct
pairing of bases?
(a) adenine with thymine
(b) adenine with guanine
(c) thymine with adenine
(d) guanine with cytosine
(e) thymine with thymine
21. Question 3
DNA molecules are formed from
(a) organic bases
(b) amino acids
(c) deoxyribose
(d) nucleotides
22. Question 4
Which of the following are organic bases?
(a) Valine
(b) Guanine
(c) Thymine
(d) Serine
