Every cell in the human body has DNA tightly packed into compact structures.
In unisexual organisms, chromosomes can be distinguished into autosomes and allosomes.
Autosomes or somatic chromosomes carry genes that determine bodily characteristics; they are homologous pairs that transfer genetic information from parents to offspring.
Each pair of chromosomes contains all the genes responsible for the existence of life.
The chromosomes are the same length in each pair, with the centromere positioned in the same place.
During mitosis, these chromosomes are duplicated, and information is transferred to two daughter cells.
Then, the new daughter cells get a complete copy of the chromosomes that contain the parent cell’s genetic information.
Autosomes are labeled 1 through 22 based on the number of base pairs present.
Although autosomes are not sex chromosomes, they contain some genes that determine sex (male and female).
For example, the SOX9 gene on chromosome 17 activates the transcription factor encoded by the SRY gene present on chromosome Y.
This transcription factor plays a vital role in determining the male sex.
Mutations in the SOX9 gene in humans with a Y chromosome lead to the development of female offspring.
Allosomes or sex chromosomes
The 23rd pair of chromosomes present in humans are called allosomes. They differ in size and function compared to autosomes.
Allosomes are sex chromosomes that carry genes responsible for sexual characteristics and, as such, have a significant role in determining the sex of an individual.
They are labeled with the letters (X and Y).
Allosomes in women comprise two X chromosomes; in most cases, the two allosomes in the female are identical. In the male, the allosome is similar to that of the female and is designated as X. The other differs morphologically and genetically. It is defined as Y.
- The Y chromosome, in most cases, is smaller than the X chromosome.
- The Y chromosome, in particular, determines the male sex.
In addition to their role in sex determination, allosomes also play an essential role in sex-linked inheritance.
The unusual combination of allosomes produces disorders such as color blindness, hemophilia, and fragile X syndrome.
Each gene present in autosomes is responsible for carrying out a specific function in each organism cell.
Under normal circumstances, each chromosome follows a “map” shared among the species’ individuals. This map is used by the factors that affect gene expression to respond to the needs of each cell with great precision.
This will allow cells to begin gene expression in the right place and at the right time where a particular gene should be expressed. Each cell contains the necessary information that the whole organism can reproduce with its complement.
Autosomes can undergo transfers when they break. These pieces come together in the wrong place, causing problems in the expression of genes, causing diseases such as cancer, and leading to errors in cell development and reproduction.
Genetic disorders are diseases caused by abnormalities in the genetic makeup of an individual, and the vast majority are inherited from parents to children.
There are many different types of genetic disorders; A congenital disease can be caused by a mutation in one section of the gene, an absence or alteration in an entire chromosome, or a variety of individual modifications influenced by genetic factors.
In addition to the fact that the number of genes affected changes the disease, whether the trait involved is dominant or recessive also makes a difference in risk factors and susceptibility, particularly how easy it is to pass the genetic disorder onto your skin. Offspring.
An autosomal dominant genetic disorder
If a genetic disorder is autosomal dominant, that means that only one parent needs to have the congenital disease for the offspring to have it as well.
Since the genetic trait is dominant, the abnormal gene will override the normal gene if passed on instead of a recessive trait, which requires two genes.
This works the same way as a genetic trait like eye color; brown eyes are a dominant gene, so you can have them with just one brown eye, while blue eyes are recessive and require two genes.
In the case of a genetic disorder, assuming your parent has only one gene with the abnormality (it is possible to have two with many genetic diseases), you have a fifty percent chance of receiving the abnormal gene.
Among some of the cases of disorders linked to the autosomal dominant inheritance, we have:
- Hyperimmunoglobulinemia E syndrome due to mutations in STAT3 (Job’s syndrome).
- Warts, Hypogammaglobulinemia, Infections, and Myelotetraxia forms of neutropenia (low neutrophil counts) (Whim syndrome).
- DiGeorge syndrome .
- Some unusual forms of defects in the interferon-y and interleukin-12 pathway.
Autosomal recessive genetic disorder
When an individual is born to parents who possess a particular mutation or information in an autosomal recessive gene, the expected outcome for each pregnancy is:
- There is a 25% chance that the child will be born with two normal genes (standard).
- There is a 50% chance that the child will be born with one normal and one abnormal gene (carrier, no disease).
- A 25% chance that the child will be born with two abnormal genes (at risk for the disease).
Among some of the cases of disorders linked to autosomal recessive inheritance we have:
- Severe combined immunodeficiency.
- Chronic granulomatous disease.
- Ataxia Telangiectasia or Louis – Bar syndrome.