Chromosomes are made of 50% proteins (structure, protection, turn genes on and off), and 50% DNA (deoxy-ribonucleic acid).

Chromosomes are made of many chromatin threads, each containing DNA and proteins.

Somatic cells contain 46 chromosomes, gametic cells contain 23 chromosomes.

44 of our chromosomes are AUTOSOMES, while 2 are called sex chromosomes.

Each chromosome contains many GENES that act as a blueprint or set of instructions for the cell.




The DNA in chromosomes forms the basis for the genetic code. It alone contains the language of life that determines how a cell operates and all of your characteristics.

DNA is made of long chains of nucleotides. DNA has a DOUBLE-HELIX structure where 2 strands of nucleotides join and twist around to form a spiral staircase or twisted ladder.




Each nucleotide has 3 parts:

1. a phosphate group - helps form the backbone of the DNA molecule

2. a sugar (deoxyribose) - acts as a glue,forms the backbone with phosphate

3. nitrogen bases - 4 types (guanine, cytosine, adenine, thymine)






LAW OF COMPLEMENTARY BASE PAIRINGS: adenine and thymine always bind to one another (A-T) and cytosine and guanine bind together (C-G).















Thus the double helix DNA has the complementary bases hidden and protected by the intertwined sugar-phosphate backbones.




  1. Control of cell activities: to produce characteristics of an individual and species
  2. Replication: in order for materials to be passed on from cell to cell, generation to generation, and for growth, via meiosis and mitosis.
  3. Undergo mutations: permanent changes passed onto offspring may advance the species via evolution