TYPES OF MAJOR GENETIC OR CHROMOSOMAL MUTATIONS - ANATOMY AND PHYSIOLOGY - 2025

The types of genetic or chromosomal mutations are varied. They refer to alterations in the order or number of genes within chromosomes. These could be passed on to the offspring if they affect the eggs and sperm.

If this is the case, it is an inherited mutation, but if it occurs without the parent having the mutation, it is a de novo mutation.

Generally, genetic mutations occur during gamete formation in meiosis and are due to broken or poorly repaired DNA strands.

Chromosomal mutations may or may not have visible effects for people. These effects can vary according to where they occur and whether they affect the function of proteins or related processes.

The human being has 23 pairs of chromosomes (half inherited from the mother and the rest from the father). Many times, genetic mutations can only be discovered with the support of microscopic techniques and after long investigations.

Most important types of genetic mutations

There are different classifications of genetic mutations depending on the element that is affected. One of the classifications describes 3 main types of mutations: molecular, chromosomal, and genomic.

1- Molecular mutation

They are the mutations that affect the chemical composition of genes.

2- Chromosomal mutation

It is a mutation in which what changes is a part of the chromosome.

There are different classifications depending on what they affect. If they affect the number of genes, it can be in the form of:

- Duplication

It occurs when a part of the chromosome is repeated within the same chromosome. It is the type of mutations that is related to the evolutionary process of species.

- Deletion

In this case, a portion of the chromosome is lost. Its severity depends on the number of genes in the missing portion. If the individual is homozygous, this mutation is fatal.

If chromosomal mutations affect the order of genes, we talk about:

- Investment

This genetic alteration occurs when a part of the chromosome separates to rejoin later, but in the opposite direction. If an inversion occurs, the gametes are likely not viable.

There are two types of investments:

Pericentric: they change the shape of the chromosome because they affect the centromere (the point of union between the chromatids that make up the chromosome).

Paracentric: they do not affect the centromere at all; therefore, they do not alter the shape of the chromosome either.

- Translocation

It implies that a part of the chromosome changes position, location. If that change occurs within the same chromosome, it is a transposition. If it occurs between different chromosomes, it is called a translocation.

A translocation affects the offspring because it implies that they will inherit a duplicate or incomplete chromosome.

There is a special type of translocation known as the Robertsonian translocation, in which two non-homologous chromosomes join their long arms at the centromere, forming a single chromosome.

3- Genomic mutation

It is a mutation in which the entire genome is affected by increasing or decreasing the chromosome sets or chromosomes.

Other types of genetic mutations

Another classification of mutations divides them into:

1- Silent mutations

One of the bases of DNA is modified while still coding for the same amino acid.

2- Polymorphisms

In this case one of the DNA bases also changes, but the function of the protein is not impacted to a degree that can cause disease. If the same mistake is repeated very close to each other, it can degenerate into a pathology.

3- missense mutation

In the case of this mutation, the change in one of the bases of the DNA implies that an amino acid different from the one it should be encoded is encoded. Coding for the wrong amino acid can alter the function of the protein.

4- Nonsense mutation

This is a mutation in which the chain of amino acids is truncated. Depending on where the breakdown occurs, it could end protein formation.

5- Insertion

In this case, more bases are added to the original DNA base, which can affect the reading frame. It also occurs when inappropriate amino acids are inserted.

6- Ring chromosome

When the arms of a chromosome fuse together in a ring, it is called a ring chromosome. It is a rare disorder that is related to diseases such as Turner syndrome.

7- Isochromosome

This mutation occurs when a chromosome loses one arm but has the other duplicated. It usually occurs when the centromere divides transversely.

8- Marker chromosome

In this case it is a small chromosome made up of parts of one or more other chromosomes. Its frequency is low and its origin is unknown.

8- Uniparental disomy

It is a mutation that implies that both chromosomes of one of the 23 pairs that DNA has, come from the same parent.

Therefore, the chromosome of one of the two parents will be duplicated, while the other will be absent.

It can be the mother (maternal uniparental disomy) or the father (paternal uniparental disomy). Uniparental disomy can lead to diseases such as Angelman syndrome.

Causes and consequences of genetic mutations

Although many of the chromosomal mutations have an origin that is still unknown to science, more and more studies are showing revealing results about the way in which lifestyle habits affect their appearance.

Smoking, for example, has been linked to the appearance of multiple chromosomal mutations. A study published in the journal Science revealed that smoking a pack of cigarettes a day can cause 150 mutations a year in each cell of the lung, 97 mutations in the larynx, 23 mutations in the mouth, 18 mutations in the bladder and 6 mutations in the liver.

Genetic mutations are usually related to malformations or defects in the regular functioning of an organism, but they also have to do with evolutionary modifications that make it possible for a species to survive.

References

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2. BBC World. Tobacco causes hundreds of genetic mutations in smokers (and they don't go away if you quit). Recovered from: bbc.com
3. Biology (s / f). Chromosomal or structural mutation. Recovered from: biología-geologia.com
4. E-ducative (s / f). Genetic material can change. Chromosomal mutations. Recovered from: e-ducativa.es
5. Scientific Eye (2015). 5 rare genetic mutations that surprise. Recovered from: informe21.com
6. wikipedia.org