DNA stands for deoxyribose nucleic acid
This chemical substance is present in the nucleus
of all cells in all living organisms
DNA controls all the chemical changes which
take place in cells
The kind of cell which is formed, (muscle, blood,
nerve etc) is controlled by DNA
Genes are composed of very long strands of DNA the
total length of DNA in each cell is about meter.
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:
1. Phosphate group
2. Pentose sugar
3. Nitrogenous base
The function of DNA is carrying huge amount of
information that determine all biological of organism
and which is transmitted from one generation to next
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
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.
Chromatin- DNA histone material is chromatin. The
chromatin is supercoilled and packaged into the
Histone- the double helix itself twisted wrapped in a
highly organized way around structural protein called
Centromere-is a region of DNA i.e. is responsible for
the movement of the replicated chromosome into the
two daughter cell during mitosis & meiosis.
Telomere- to protect end of chromosome.
Diploid cells contain both
parental chromosomes. (Ex.
every cell other than sex cells in
•Haploid cells contain half of
the parents chromosomes. (Ex.
sperm and egg cells are
What is a Homologous Chromosome?
Homologous chromosomes are the same size and
shape carrying the same genes for the same traits. One
comes from the father one from the mother.