The Nucleus (2) : DNA chain


.The DNA chain is a sequence of nucleotides that form a solid skeleton for the information storage where the deoxyribose is joined by the esterified phosphates between positions 5' and 3'.

The links are covalent phosphodiester.

  • The nitrogenous bases

They can be separated into two groups:

On one hand, the purines, that are composed of two rings: Adenine and Guanine

On the other hand the pyrimidines, that only have a ring: Thymine and Cytosine.

The DNA, as we have already stated, is the stocker of the genetic information.

The alpha-helices: DNA chains are aligned so they are in an antiparallel way, which forms a helical. That spiral is due to the hydrogen bonds between the nitrogenous bases.

Those bonds are the following

Adenine-Thymine : 2 bonds of Hydrogene

Guanine-Citosine: 3 bonds of hydrongene

The info genetics is stored in the sequence of nucleotides. Therefore, what is gen?

A gen is a portion or segment of DNA. Each gen codifies for a particular protein. 

GENOMA:  It's the set of genetic information, transmitted in a hereditary way, the whole assemblage of genes, the sum of the complete DNA.

Individual genoma: All the information contained in a group of halode chromosomes.

Specie's genoma: the population of a species shares the genes, and most of the information contained in each one, with subtle differences, therefore, each species has a content of similar genetic information.

The complexity of the genome comes from the variety of DNA sequences that compose it, and the number of copies of these sequences.

 3 types of DNA sequences 

Highly repetitive ("satellites" ,"mini-satellites" and "microsatellites").

Repetitive: some with coding function: RNA, histones, and others without coding function.

Unique sequences: most coding sequences.