Red Blood Cells

The red blood cells (or erythrocytes) are the principal component of the blood: they are round organelles, of microscopic size, all equal, full of a liquid substance, the haemoglobin, which gives to the blood its red colour, when combined with oxygen. It is absolutely essential for the life, since it is the substance that delivers oxygen to all the cells of the organism.

Haemoglobin Molecule

It is an assembly of 4 globin chains different among them for the arrangement of the aminoacid molecules that compose it. These chains are countersigned with the Greek letters: α(alpha), β (beta), δ (delta), γ (gamma).

Types of haemoglobins

There are three types of normal haemoglobin. In adult humans the haemoglobin (A) constitutes the 98% of total haemoglobin and is composed from 2 α and 2 β globin chains. It is proper of the individual after the birth. The haemoglobin A₂, is composed from 2 α and 2 δ chains. The δ chain synthesis begins late in the third trimester and continues into adulthood at a normal level of 2%. The foetal haemoglobin (F) is composed from 2 α and 2 γ chains, it is proper of the intrauterine-life period.

Globin Genes

Globin genes bring all the genetic information to allow the production of the proteins composing the haemoglobin.

The DNA of normal individuals contain one or two pairs of structural genes for each globin chains (α, β, δ, γ) regulating the globin production and inherited half by the father and half by the mother, as each hereditary character. Their children, in the following offspring, will transmit again, according to the laws of Mendel.

Location and organization of the globin genes

The globin genes are located with a well precise distribution on the chromosomes 11 and 16. The genes ε (epsilon) and ζ (zeta) constitute the genes of the β group and of the α group respectively active in the first phase of the intrauterine life.

Each globin gene consists of 3 coding sequences, termed exons (which are transcribed into the mRNA and thereafter translated into the globin) and 2 non-coding regions, known as introns or InterVening Sequences (IVS: which are untranscribed and thereby no globin chains are produced; however they have regulation functions). In the Figure, the white color represents the pseudo-genes. They do not develop neither synthetic activity neither regulation one. The DNA molecule is transcribed (or neo-synthesized) forming an identical molecule of pre-mRNA. This product is modified by a complicate mRNA maturation process (processing) at the end of which the mature mRNA is definitively established in the structure. An important phase of this maturation process is represented by excision and release events of the introns (splicing).

The mature mRNA, after being delivered by the nucleus to the cell cytoplasm, is translated into globin chain.