1
,2
,DNA: THE CODE OF LIFE
Paper 2: 27 marks
GUIDE ON HOW TO TACKLE THE TOPIC.
Introduction
Revision of the structure of the cell with an emphasis
on the ribosome, cytoplasm, and the parts of the
nucleus
Two types of nucleic acids: DNA and RNA
Nucleic acids consist of nucleotides
DNA: location, structure ,and functions
Location of DNA:
Present in the nucleus (nuclear DNA) – makes up
genes on chromosomes
Present in mitochondria (mitochondrial DNA)
Present in chloroplasts (plants)
Brief history of the discovery of the DNA molecule
(Watson & Crick, Franklin & Wilkins)
Structure of DNA
The natural shape of the DNA molecule is a double
helix
Each strand of the helix is made up of a sequence of
DNA nucleotides.
3
Juniour Bela
, Three components of a DNA nucleotide:
Nitrogenous bases linked by weak hydrogen bonds:
Four nitrogenous bases of DNA:
1. adenine (A)
2. thymine (T)
3. cytosine (C)
4. guanine (G)
Pairing of bases in DNA occurs as follows:
*A and T
*G and C
Sugar portion (deoxyribose in DNA)
Phosphate portion
Stick diagram of DNA molecule to illustrate its structure
Functions of DNA:
DNA makes up genes which carry hereditary information
DNA contains coded information for protein synthesis
DNA profiling
Interpretation of DNA profiles
Uses of DNA profiles
80%
4
Juniour Bela
,2
,DNA: THE CODE OF LIFE
Paper 2: 27 marks
GUIDE ON HOW TO TACKLE THE TOPIC.
Introduction
Revision of the structure of the cell with an emphasis
on the ribosome, cytoplasm, and the parts of the
nucleus
Two types of nucleic acids: DNA and RNA
Nucleic acids consist of nucleotides
DNA: location, structure ,and functions
Location of DNA:
Present in the nucleus (nuclear DNA) – makes up
genes on chromosomes
Present in mitochondria (mitochondrial DNA)
Present in chloroplasts (plants)
Brief history of the discovery of the DNA molecule
(Watson & Crick, Franklin & Wilkins)
Structure of DNA
The natural shape of the DNA molecule is a double
helix
Each strand of the helix is made up of a sequence of
DNA nucleotides.
3
Juniour Bela
, Three components of a DNA nucleotide:
Nitrogenous bases linked by weak hydrogen bonds:
Four nitrogenous bases of DNA:
1. adenine (A)
2. thymine (T)
3. cytosine (C)
4. guanine (G)
Pairing of bases in DNA occurs as follows:
*A and T
*G and C
Sugar portion (deoxyribose in DNA)
Phosphate portion
Stick diagram of DNA molecule to illustrate its structure
Functions of DNA:
DNA makes up genes which carry hereditary information
DNA contains coded information for protein synthesis
DNA profiling
Interpretation of DNA profiles
Uses of DNA profiles
80%
4
Juniour Bela
