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Types of Mutations: Substitution, Insertions, Deletion and Frameshifts - Printable Version

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Types of Mutations: Substitution, Insertions, Deletion and Frameshifts - NatashaKundi - 07-18-2010

A mutation is a permanent change in the DNA sequence of a gene. Sometimes mutations can be useful but mostly they are harmful as changes in DNA can change the way a cell behaves. As genes are a set of hereditary materials that contain instructions necessary for a cell to work so if some of these instructions go wrong the cell may not know how to function.

Mutations can be inherited which means the mutated genetic code can be passed on to the next generations. For example heart disease, diabetes, stroke or high blood pressure, run in the family. If parents suffered from them, their children may also develop them. Ten million men in the U.S. are colour blind but less than 600,000 American women have the same disability. That's because this mutation is located on the X-chromosome. Men only have one X-chromosome, so that one is enough to induce the condition, but women have two X chromosomes, and they require the mutation in double set to experience the condition.

Mutations can also be acquired depending on what sort of environment a person lives in as some environmental agents can damage the DNA or when mistakes occur during cell division. For example radiations released during the nuclear disasters in Hiroshima and Nagasaki and Chernobyl are still affecting and causing mutations in the genetic makeup of the people living in those areas. Moreover, different types of cancers are also caused by mutations.

Types of Mutation:

Substitution

A substitution is a mutation in which there is an exchange between two bases (i.e. a change in a single "chemical letter" such as switching a T to a C). Such a substitution could change a codon to one that encodes a different amino acid and cause a change in the protein produced. Sometimes substitutions may not effects the protein structure, such mutations are called silent mutations and sometimes they may change an amino-acid-coding codon to a single "stop" codon and cause an incomplete protein. This can seriously affect the protein structure which may completely change the organism.

Example of Substitution Mutation: Sickle Cell Anaemia is caused by substitution mutation, where in codon (GAG mutates to --> GTG) and leads to (Glu --> Val) change.


Insertion

Insertions are mutations in which extra base pairs are inserted into a new place in the DNA. The number of base pairs inserted can range from one to thousands!

Example of Insertion Mutation: Huntington's disease and the fragile X syndrome are examples of insertion mutation wherein trinucleotide repeats are inserted into the DNA sequence leading to these diseases.

Deletions

Deletions are mutations in which a section of DNA is lost, or deleted. The number of base pairs deleted can again range from one to thousands!
Insertions and Deletion mutations are often together dubbed as INDELS.


Example of Deletion Mutation: 22q11.2 deletion syndrome is caused by the deletion of some bases of chromosome 22. This disease is characterized by cleft palate, heart defects, autoimmune disorders etc.

Frameshift

Protein-coding DNA is divided into codons which are three bases long, insertions and deletions in these codons can completely change a gene so its message cannot be decoded correctly. Such mutations are called frameshift mutations. For example, consider the sentence, "The cat ate her rat." Each word represents a codon. If we delete the first letter and read the sentence in the same way, it doesn't make sense. Similarly if the codons become jumbled up, they would no longer make any sense, in such frameshifts, a similar error occurs at the DNA level, where the codons cannot be parsed correctly. This usually gives rise to truncated proteins that are as useless as "rca tet hce tee" is uninformative.

Examples of Frameshif Mutation:
Tay-Sachs Disease, Cancers of many types, Crohn's Disease, cystic fibrosis have been associated with Frameshift Mutation.

Following Video describes the various types of mutations in a very nice way:






RE: Types of Mutations: Substitution, Instertion, Deletion and Frameshifts - Amna82 - 07-20-2010

A very good description about the types of mutations. A person who is doing an assignment or project about the mutations, this article will be of great help. Keep it up Natasha!


RE: Types of Mutations: Substitution, Instertion, Deletion and Frameshifts - ExpertScie - 10-04-2012

Mutations, is the change in the blue print of life and that blue print is our DNA in which all phenotypic expressions are coded. The Biotechnologist and researches in this field had today discovered that mutation does not only change the appearance but are involved in behavior of men and women’s!

Recent studies in this field had shown that with the mutation of BRCA gene (BRCA1 and BRCA2), lead young women’s to take complex decisions about life plans and feel differently about their view for treatment, relationship, childbearing as well as career! Thus it is very interesting fact that mutations are also involved in psychosocial consequences. Mutations had lead to human evolutions and may be to the evolution of their behavior which are being proved today with the studies of BRCA gene mutations and many other which are in progress! Also the type of mutations leads to chances of different types of diseases like women with inherit BRCA 1 mutation have increased risk of developing cancers related to breast & ovarian. While the mutation in BRCA2 gene leads to increase in risk of cancer of pancreas, stomach and gall bladder. Therefore research in mutation are helping to better understand its impact well in advance and thus helping scientists to cure and prevent related diseases.

Even though Mutation occurs but Survival of the species demands genetic stability! In nature, Mutations occurs but very rarely it remains uncorrected, because DNA, RNA replication and sequence are maintained with a very high fidelity. Even a small change in sequence gets corrected by the DNA repair mechanism. Most of the mutations are deleterious and are eliminated by natural selection process and mutation rate. Changes in hereditary instruction had shown the way of evolution on earth. Mutation is unpredictable. If mutation occur in somatic cells then that will not get pass on to next generation but if occurs in germile cells then it will fatal, as this may pass on to next generation.

Mutations are broadly categorized in six ways as Point mutation-change will occur in one gene sequence. Frame shift mutation -change occur as addition or deletion of one or more base sequence in gene, Deletion mutation-this mutation is more or less related to frame shift mutation but in this more bases deleted which may affect large number of genes in chromosome, Insertion mutation- is the addition of additional bases in gene, Inversion mutation- Entire DNA strand get inverted or say all base sequence get reversed, DNA expression Mutation- causes the variation in DNA expression process , so less or more protein get synthesized !


RE: Types of Mutations: Substitution, Insertions, Deletion and Frameshifts - bridgettpayseur - 08-09-2013

This is a very informative post. I would just like to make a few clarifications and additions to help students coming to get information.


There are three types of base-substitution mutations. As the original poster noted, when a base substitution mutation does not change the amino acid inserted into the gene, it is called a “silent mutation.” When the base substitution does change the amino acid, this is called a “missense mutation.” When the substitution results in a stop codon being inserted, this is called a “nonsense mutation.” I remember this by thinking that “nonsense” is similar to saying “no more”, so the protein is ended.


Insertion and deletion mutations can result in frameshift mutations, when the reading frame of the gene is changed. This frameshift only happens when the insertion or mutation is not a multiple of 3 nucleotides. For example, look at the sentence:

The big red pig ate the ham.


If we insert 2 letters, the frame is shifted.

The big rec adp iga tet heh am.


If we insert 3 letters, the frame is not shifted; however, an extra amino acid is added, which changes the sentence.

The big red cat pig ate the ham.


Insertion and deletion mutations can be as small as one nucleotide, to thousands of nucleotides long. These long insertion or deletion mutations normally occur when one part of a chromosome crosses over and changes genetic information with a different chromosome.


All mutations have the potential to be very damaging, but most are benign. Mutations are an important part of evolution, allowing us to develop adaptations and diversity.