The dogma centra of molecular biology

1) The concept of genes is historically defined on the basic of genetic inheritance of a phenotype. (Mendellian Inheritance)

2) The DNA an organism encodes the genetic information. It is made up of a double stranded helix composed of ribose sugars. 

Adenine(A), Citosine (C), Guanine (G) and Thymine (T).

[note that only 4 values nees be encode ACGT.. Which can be done using 2 bits.. But to allow redundant letter combinations (like N means any 4 nucleotides), one usually resorts to a 4 bit alphabet.]

3) Each side of the double helix faces it´s complementary base.

A-T, and G-C.

4) Biochemical process that read off the DNA always read it from the 5´´side towards the 3´ side. (replication and transcription).

5) A gene can be located on either the ´plus strand´ or the minus strand.  But rule 4) imposes the orientation of reading .. And rule 3 (complementarity) tells us to complement each base E.g.

If the sequence on the + strand is ACGTGATCGATGCTA, the – strand must be read off by reading the complement of this sequence going ´backwards´

e.g. TAGCATCGATCACGT

6) DNA information is copied over to mRNA that acts as a template to produce proteins.

 

 

We often concentrate on protein coding genes, because proteins are the building blocks of cells and the majority of bio-active molecules. (but let´s not forget the various RNA genes)

source from :
Hugues Sicotte NCBI Fundamentals in Sequence Analysis 1.(part 1) and http://crystal.uah.edu/~carter/protein/dogma.htm