During our biology lesson, we learn the followings:
Chromosomes can be found in the nucleus of a cell.
Each chromosome is made up of a long DNA molecules coiled around protein molecules called histones.
A DNA molecule contains thousand of genes which code for the synthesis of specific proteins.
What is DNA molecule?
DNA molecule is made up of basic units called nucleotides.
A nucleotide is made up of:
1. a deoxyribose sugar,
2. a nitrogenous base (Adenine, Thymine, Cytosine or Guanine),
3. a phosphate group
How are the nucleotides linked?
Each nucleotide is joined to the next nucleotide through the phosphate group to form a long polynucleotide strand.
A DNA molecule consists of two polynucleotide strands coiled together to form a DOUBLE HELIX.
The two strands are linked together at the nitrogenous base by hydrogen bond. Thymine base is linked to Adenine base, while Cytosine base is linked to Guanine base.
In 1953 James D. Watson and Francis Crick suggested what is now accepted as the first correct double-helix model of DNA structure.
The sequence of nitrogenous base in a DNA molecule is called gene.
What is gene? It is a DNA segment containing particular sequence of nucleotides that code for synthesis of a specific polypeptide chain or proteins in an organism.
Proteins are needed to form enzymes & other structural proteins in an organism.
Gene control the traits of an organism by controlling the types of proteins to be synthesised in cells.
