What are Autosomal Chromosomes?

The Autosomal chromosomes Are all chromosomes that have no sexual characteristics. In humans, they go from chromosome 1 to chromosome 22, since chromosome 23 is the one that delivers sexual characteristics and differs in X and Y.

Humans have 44 autosomal chromosomes or autosomes, since they are always found in pairs, being the human diploid genome. More alosoma 23 - that is, chromosome with sexual characteristics - the human genome is made up of 46 chromosomes in total.

Autosomic and sexual chromosomes

Characteristics of the autosomal chromosomes

The autosomes are not always the same size. The largest autosome is Chromosome 1- containing 2800 genes, followed by Chromosome 2- which has 750 genes inside.

Usually, each of the diploid sets of chromosomes are inherited from each parent. The autosomes are listed in numbers 1 to 22, approximately in relation to the size of the pairs, whereas the allosomes are classified with the letters X or Y. Females have two X chromosomes (XX) while males have one of each One (XY).

However, autosomes may have sex-determining genes without being specifically a chromosome with sexually identifying features such as X chromosomes or Y chromosomes. The genes come in pairs, one gene from each pair belongs to the mother and the other gene to father.

All human autosomes have been extensively screened and identified through extraction of cellular chromosomes and then stained with some type of dye, usually Giemsa. With this it is possible to develop a cytogenic map or cariogram, where each chromosome is indicated in the form of number, size and shape in an ordered manner.

Through these studies, it is possible to identify genetic abnormalities in certain chromosomes that cause diseases of hereditary transmission, as is the case of Trisomies .

By identifying the chromosomes that possess these alterations, it is possible to trace the beginnings of a disease Or syndrome and with this can provide solutions and preventive treatments.

Genetic disorders in autosomes

Genetic disorders of autosomes can occur for multiple causes. The most common are a defect in the separation of homologous cells, which correspond to the fecundation cells of the parents or the transmission through Mendelian inheritance of a gene that has a dominant pattern. This is known as dominant autosomes and recessive autosomes:

Autosomal dominant inheritance

In this type of disease, defects can be transmitted to children of both sexes, and usually one of the parents also manifests the disease. The child in this case must inherit only a copy of the damaged allele to manifest the disease.

A single autosomal abnormality, within the 22 autosomes that correspond to the chromosomes of each parent, can cause an autosomal dominant disorder. If this autosoma is dominant, even if the other parent is normal, it will dominate its presence in the child's genome.

However, this can also occur as a new condition, in the event that neither parent has the abnormal gene.

If a parent has an autosomal dominant disorder, he or she has a 50% chance that the same disorder will be transmitted to your child. This occurs in each of the pregnancies and regardless of whether one of the siblings already has the condition.

On the other hand, if a child of a patient who carries a dominant autonomic disorder does not inherit the abnormal gene, it will neither develop nor pass the disease.

Some examples of autosomal dominant disorders are Huntington's disease and the Marfan syndrome .

Autosomal recessive inheritance

In this case, it is necessary that two copies of an abnormal gene are present so that the disease or syndrome can occur and develop in the child.

If a patient suffers an autosomal recessive inheritance disorder, it means that each of their parents carried a copy of the defective gene, but none of them showed signs or symptoms related to the disease or syndrome.

These types of disorders are not found in every generation of a family. In fact, a person has a four-way possibility of inheriting the abnormal gene from both parents and developing the disease or mutation. In contrast, there is a 50% chance of inheriting the abnormal gene from one parent or the other.

In the case of a pregnancy, there is a 50% chance that the child will inherit one of the abnormal genes and have other normal genes; And a 25% chance that none of the abnormal genes will come - or that, on the other hand, get the two genes mutated and develop the disease.

Some examples of autosomal recessive diseases are cystic fibrosis and the Sickle cell anemia .

Aneuploidy of autosomes

Aneuploidy is the second largest category of chromosome mutations and occurs when the number of chromosomes is abnormal. That is, an organism with aneuploidy has a different number of chromosomes than its original set of chromosomes. The most common aneuploidies are trisomies and monosomies.

This is usually due to a failure in the separation phase of the cell, ie a delay during the process of meiosis of the chromosome.

However, the most common cause is non-meiotic disjunction. During the process, two chromosomes are left together and one pole is empty. It is more common to occur during meiosis than mitosis, but it can occur in both processes.

In the case of trisomy, one of the most frequent is the trisomy of chromosome 21, which gives rise to individuals with Down's Syndrome , A condition with specific characteristics such as growth delays, distinctive facial features and some moderate intellectual disability. Other known trisomies are autosoma 13 or 18. Many of them are not compatible with life.

Although the cause of aneuploidy is not really known, maternal age has always been one of the factors to consider. This occurs because women's oocytes are the same age and with aging cells can decrease their ability to maintain chromosomal tetrad during the process of meiosis.

It should be noted that the greatest number of chromosomal abnormalities occur in autosomes. Therefore, a comprehensive study of genes will prevent and prevent inherited genetic disorders and diseases.

References

  1. Medical definition of autosomal chromosome. Retrieved from medicinenet.com.
  2. Retrieved from Wikipedia.com.
  3. How many autosomes do humans have? Retrieved from reference.com.
  4. Autosomal dominant. Retrieved from medlineplus.gov.
  5. What are the different ways in which a genetic condition can be inherited? Retrieved from ghr.nlm.nih.gov.
  6. An Introduction to Genetic Analysis. 7th edition. Retrieved from ncbi.nih.gov.
  7. Autosomal Abnormalities. Retrieved from anthro.palomar.edu.

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