Chromosomal Mutations: In living organisms, mutations occur at a rate one per every ten million cell replications. And as compared to the more than 100 trillion cells in the human body, this number is rather insignificant.
Chromosomes are thread-like structures where the genetic material DNA is packaged. They are located in the nucleus of cells and undergo condensation before cell division. Like any other processes, the chromosome may encounter random genetic changes or be affected by it.
In this article, we will explore as what happens when a chromosome encounters such changes in its structure, number, and type.
Table of Contents
- What is a Chromosomal Mutation?
- Structural Chromosomal Mutations
- Chromosomal Number Mutations
- The Advantages of Chromosomal Mutations
- The Disadvantages of Chromosomal Mutations
What is a Chromosomal Mutation?
- Unlike gene mutations that involve the alteration of a gene or a segment of DNA in the chromosome, chromosomal mutations occur and change the entirety of the chromosome itself.
- Three types of chromosomal mutations exist: mutations on the structure of chromosomes, mutations on the chromosome number, and mutations on the sex chromosomes.
Structural Chromosomal Mutations
This kind of chromosomal mutation usually occurs during any errors in cell division. This happens when homologous chromosomes paired up, genes in chromosomes broke apart, genes inserted in the wrong chromosome, or genes or set of genes are completely lost in the chromosome.
Basically, structural chromosomal mutations are classified into four: deletion, duplication, inversion, and translocation (or shift places). They are illustrated below:
Disorders Due To Deletion
Common disorders due to deletion mutation in humans are: Cri du chat, Duchenne muscular dystrophy, Di George’s syndrome, etc.
- This duplication can now supply additional material that has the ability to evolve new functions.
Disorders Due To Duplication
Common disorder due to duplication mutation in humans is: Charcot-Marie-Tooth disease type I.
- During a pericentric inversion, the inversion encompasses the centromereWhat is Centremere?The Centromere is a constriction in a chromosome; at one point along its length dividing it into a shorter arm, called the p arm, and a longer arm, called the q arm. of the chromosome.
- On the other hand, during a paracentric inversion, it only involves either the short or long arm of the chromosome and the inversion point does not include the centromere.
Disorders Due To Inversion
Common disorder due to inversion mutation in humans is: Amniocentensis during pregnancy.
Disorders Due To Translocation
Common disorders due to translocation mutation in humans are: XX male syndrome, Down syndrome, Infertility and Cancer.
Chromosomal Number Mutations
- The naming of aneuploid conditions is generally based on the number of chromosomes added or deleted. For instance, a monosomic (2n -1) individual bears only one copy of a chromosome, instead of having two.
- Other variations of aneuploidy are trisomic (2n+1), nullisomic (2n-2), and disomic (n+1).
- Interestingly, polyploidy is a common phenomenon among plants as well as certain groups of fish, salamanders, frogs, and leeches.
The Advantages of Chromosomal Mutations
Believe it or not, the random errors that occur during cell division can be beneficial for organisms. Listed below are some of them.
- In humans, some successful mutations include malaria resistance, lactose tolerance, and atherosclerosis tolerance.
- And clearly, without genetic diversity, some of the fundamental mechanisms of evolutionary change cannot (and continue to) operate.
- Examples: As some chromosomal mutations are harmless, humans get different color eyes such as black, brown, grey, green or blue.
The Disadvantages of Chromosomal Mutations
Some mutations can be quite detrimental as well. The following are the some of the most common disadvantages of mutations in the chromosomes:
1. Genetic Disorder
2. Other Diseases
No matter what we do, the random changes in our genome are highly inevitable. And in this case, does the saying “the only constant is change” proves true?
-  – “What is a chromosome? – Genetics Home Reference”. Accessed March 29, 2017. Link.
-  – “Deletion Mutation: Definition, Examples & Diseases – Video & Lesson Transcript | Study.com”. Accessed March 29, 2017. Link.
-  – “Duplications – An Introduction to Genetic Analysis – NCBI Bookshelf”. Accessed March 29, 2017. Link.
-  – “Chromosome Mutation”. Accessed March 29, 2017. Link.
-  – “Aneuploidy – An Introduction to Genetic Analysis – NCBI Bookshelf”. Accessed March 29, 2017. Link.
-  – “Polyploidy | Learn Science at Scitable”. Accessed March 29, 2017. Link.
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