A closer look at the structure of DNA for Year 10 Science students at Saint Ignatius College Geelong

1. GENETICS.
02. The structure of DNA.
Ian Anderson
Saint Ignatius College Geelong

2. THE STRUCTURE OF DNA.
 Nucleic acids.
 Deoxyribonucleic acid (DNA).
 Ribonucleic acid (RNA).
Organisms use DNA as their genetic material to:
 Store information that determines the
characteristics of cells and organisms.
 Direct the synthesis of proteins essential to the
operation of the cell or organism.
 Replicate prior to reproduction by directing the
manufacture of copies of itself.

3. THE STRUCTURE OF DNA.
 A polymer made up of monomer units called
nucleotides.
 Each nucleotide made up of three parts.
 Sugar (Deoxyribose).
 Phosphate group.
 Nitrogen containing base.
- adenine (A) - thymine (T)
- cytosine (C) - guanine (G)

4. NUCLEOTIDES.
Source: Enger et al.
(2012)
1’
3’
5’
4’
2’

5. NUCLEOTIDES.
 Nitrogenous bases
grouped into one of two
families based on their
structure.
 Pyrimidines.
 Cytosine, Thymine (&
Uracil).
 Purines.
 Adenine & Guanine.
Source: Reece et al.
(2011)

6. THE STRUCTURE OF DNA.
 Double helix shape.
 Sugar-phosphate backbone.
 The two DNA strands are antiparallel to each other.
 DNA molecule coiled in a right handed spiral.
 Base pairing rule.
 Complementary bases.
 Adenine (A)  Thymine (T)
 Cytosine (C)  Guanine (G).
 Weak hydrogen bonds between base pairs.

7. THE STRUCTURE OF DNA.
Source: Enger et al.
(2012)

8. THE STRUCTURE OF RNA.
 Single-sided polynucleotide.
 Each nucleotide made up of three parts.
 Sugar (Ribose)
 Phosphate group
 Nitrogen containing base
- adenine (A) - Uracil (U)
- cytosine (C) - guanine (G)
 Sugar-phosphate backbone.
Source: Enger et al.
(2012)

9. THE STRUCTURE OF DNA.
 DNA molecules are very long.
 Made up of thousands to millions of base pairs.
 Each human cell contains ~2m of DNA!
 One long DNA molecule includes many genes.
 Gene = A segment of DNA that codes for the synthesis
of a particular protein.
 In humans ~20-25 000 genes.
 DNA is wrapped around histone proteins to form
chromosomes.
 Genome – the full DNA sequence of an organism.
 In humans >3 billion base pairs.

10. THE STRUCTURE OF DNA.
Source: Source: Enger et al. (2012)

11. REFERENCES.
 Enger, E.D., Ross, F.C. and Bailey, D.B. (2012).
Concepts in Biology (14th ed). Melb: McGraw Hill.
 Reece, J.B., Urry, L.A., Cain, M.L., Wasserman,
S.A., Minorsky, P.V. and Jackson, R.B. (2011).
Campbell Biology (9th ed). Sydney: Pearson
Education.

12. http://SICkScience10.wikispaces.com/