Genome = complete set of sequences in the
genetic material of an org.
Nucleic acids = Macromolecules (large RMM).
Chromosomes = Discrete unit of the genome
carrying many genes. NA and protein.
Gene = Segment of DNA specifying production of
a polypeptide chain. It codes for a RNA
• Genotypic = Replication. Store &transmit info.
• Phenotypic = Gene expression. Control devlp of
• Evolutionary = Mutation. Changes produce
Fx…..preserving, copying and transmitting information.
Chromosomes composed of 2 macmol.
ii. Nucleic acids DNA(d) and
Structure of nucleotides..
A ) 5 carbon pentose sugar ;
RNA = Ribose, DNA = Deoxyribose.
b) A nitrogen containing base;
2 Purines (A,G) 2 Pyrimidines
RNA = CGAU, DNA = CGAT
c) A phosphate group
Watson and Crick’s model
= sugar is deoxyribose
4 types of nucleotide
base : A, C, G, T
: 2 complementary strands
where A = T, C = G in
anti parallel fashion
– "complementary“ = fitting
together of 2 molecules
with hydrogen bonds
A dinucleotide is formed
when a condensation
reaction occurs between
the phosphate group of
one nucleotide and
pentose of another
linking the 2 nucleotides
More nucleotides can be added, building up a
long polynucleotide chain.
The stability of the
double helix is due to
the large number of
covalent, H+ and
These bases always pair up in the same way.
A single strand of DNA is made of letters:
The letters make words:
ATG CTC GAA TAA ATG TGA ATT TGA
The words make sentences:
<ATG CTC GAA TAA> <ATG TGA ATT TGA>
These "sentences" are called genes
The instructions in a
gene that tell the cell
how to make a specific
protein. A, T, G, and C.
3 letter word = codon =
Fx of codon = tell the cell
how to make proteins
Start and stop codon.
Genetic code contd..
Inside the nucleus, the DNA message is copied onto
RNA. to transmit the message or genetic code.
It has 4 subunits A, T, G, C and are arranged in triplet
codes. Eg ATTGCCTAG read from left to right
ATT/GCC/TAG. Each triplet code specifies different
Eg. ATT = amino acid “X”
GCC = amino acid “Y”
TAG = amino acid “Z”
This piece of genetic code will instruct the cell to make
a protein in which X,Y and Z are joined together in