A DNA molecule consists of a twisted spiral called a double helix.
DNA is found inside genes, inside chromosomes, inside the nucleus of
a cell. Each chromosome is made up of a tightly coiled strand,
a molecule of DNA. The bases in the opposite strands are
arranged such that where there is an adenine in one strand, the
other strand has a thymine and where there is a guanine in one
strand, the other strand has a cytosine.
Each strand is made up of a sugar covalently linked to a
phosphate which is covalently linked to another sugar and so on. A
DNA strand may contain thousands to millions of these
Each sugar also has a purine or pyrimidine base attached to it
through a covalent bond.
Both of the egg and sperm hold DNA. Each child receives 23
chromosomes from its mother and 23 from its father. Every cell
except for the red blood cell carries a blueprint of DNA. A molecule
of DNA holds coded plans for thousands of proteins and the length of
the strand is called a gene.
Each strand of DNA is formed by units of phosphate (P) joined with
units of deoxyribose (D). These units alternate to make the
bases of a strand of DNA.
The two side strands are connected by the two bases. The four
possible pairs are A,T or T,A G,C or C,G.
Amino acids are the building blocks of proteins. There are about 20
amino acids that establish the character of proteins. Three of those
amino acids are phenylalanine, valine and isolencine.
What is DNA Testing and PCR?