HomeHealth articlescystic fibrosisWhat Are the Defects Caused by Point Mutation?

Point Mutation - Types, Defects, and Clinical Manifestations

Verified dataVerified data
0

3 min read

Share

A point mutation can cause alterations in the DNA or RNA. This article explains this condition in detail.

Medically reviewed by

Dr. Vishal Patidar

Published At February 9, 2023
Reviewed AtJuly 17, 2023

Introduction

A mutation is defined as an alteration in the sequence of DNA. There are various mutations, out of which point mutations are the most common. A point mutation is a type of mutation occurring in DNA or RNA (these are the cell's genetic material). The addition, deletion, or alteration of one single nucleotide base happens. DNA and RNA are made up of numerous nucleotides. The nitrogenous bases on the nucleotides are made up of five molecules: cytosine, guanine, adenine, thymine (in DNA), and uracil (in RNA). They are abbreviated as C, G, A, T, and U. There are specific sequences of nucleotides that encode all the information responsible for carrying out all the cell processes.

What Are The Types of Point Mutations?

The various types of point mutations have been mentioned below:

Substitution

A substitution mutation is the substitution of one base pair for another. It is further divided into the following three types of substitution mutations:

  • Nonsense.

  • Missense.

  • Silent.

A nonsense mutation occurs due to substituting one nucleotide, which leads to the formation of a stop codon instead of a codon that codes for an amino acid. It is always present at the end of the mRNA sequence during protein production. However, if a substitution causes it to appear in a different place, it causes premature amino acid sequence termination and prevents the correct protein's production.

A missense mutation occurs due to the substitution of one nucleotide and the formation of a different codon. But, in this case, a stop codon is not formed; rather, a different amino acid is produced by the codon in the sequence of amino acids. A missense mutation is known to be conservative if the amino acid is formed because the mutation has the same properties as the actual amino acid that was supposed to be formed. If the amino has different structure and function properties, it is called non-conservative. A nucleotide substitution occurs in a silent mutation, but the same amino acid is produced. This can happen because multiple codons can code the same amino acid.

Insertion and Deletion

An insertion type of mutation happens due to adding an extra base pair to a sequence of bases, whereas a deletion type of mutation is the opposite of the insertion type. The deletion type occurs when a base pair gets deleted from a sequence. These two types of point mutations have been grouped as both can drastically affect the sequence of amino acids produced. AAA, the three-base codons can change with either the insertion or deletion of one or two bases. This phenomenon is known as a frameshift mutation. This leads to a complete change in the amino acids being produced, and thus, there can be a change in the structure and function of the resulting protein, making the resulting protein useless. Also, the sequence can shift if one base is deleted.

What Are The Examples Of Diseases Caused Due To Point Mutations?

Various diseases can be caused due to point mutations. The most common ones have been mentioned below:

Cystic Fibrosis

Cystic Fibrosis (CF) is a clinical condition characterized as a recessive inherited disorder that most commonly affects European people. Its prevalence in the United States is 1 in 3500 newborns, whereas 1 in 30 Caucasian Americans has been reported to be carriers. Various types of mutations may cause CF.

The common deletion of three nucleotides in the cystic fibrosis transmembrane conductance regulator (CFTR) gene is out of these. This leads to the loss of the amino acid phenylalanine; thus, an incorrectly folded protein is formed. This condition is clinically associated with thick, sticky mucus in the lungs, which can cause difficulty breathing, infertility in a few individuals, salty sweat, and a decreased life expectancy of about 42 to 50 years in individuals belonging to developed countries.

Sickle-Cell Anemia

Sickle-cell anemia is another point mutation recessive disorder that is caused due to substitution of a single point in the gene that functions to create hemoglobin. Hemoglobin is the main carrier of oxygen in the blood and the body. Naturally, glutamic acid is present in the chain, but the substitution replaces glutamic acid with valine.

Thin sickle-shaped blood cells are formed when people have two copies of this mutation, and these modified cells are unable to carry oxygen efficiently sometimes. The prevalence is known to almost 80 percent of affected people in sub-Saharan Africa. In this region, if the individual is a carrier of sickle-cell anemia, they are not affected by malaria.

This mutation is also found in India and the Middle East. 1 in 500 African Americans is affected by this condition. Symptoms include anemia, chest pain, and obstruction of blood vessels. It can be managed with folic acid, bone marrow transplants, blood transfusions, and prescription drugs.

Tay-Sachs

Tay-Sachs disease is another type of recessive disorder caused by point mutations. It causes the deterioration of nerve cells with time, leading to worsening physical and mental functions. All children and adults can be affected. There is no treatment available.

Conclusion

Mutations are genetic alterations and can be of various types. Point mutation is the commonest type and can be further divided into various subtypes. It can cause structural as well as functional defects. Children and adults can both get affected. The diagnosis can be made during pregnancy; if not, it can be diagnosed later in life. Although there is no definite cure, the symptoms can be managed. You can consult a specialist online with the help of various online medical platforms to know more about this condition.

Frequently Asked Questions

1.

What Exactly Is Point Mutation?

A point mutation is a genetic modification or transformation when one nucleotide base is modified, added, or removed from the DNA or RNA sequence of an organism's genome. Point mutations can have a range of effects on the downstream protein product, with predictability varying depending on the specific type of mutation.

2.

What Other Names Are Used to Refer to a Point Mutation?

A point mutation is a genetic alteration occurring when another replaces one nucleotide. It is also known as a point variant, base substitution, or substitution mutation.

3.

What Are Two Instances of Point Mutations?

Here are two instances of point mutations: 
- Three nucleotides are deleted from the CFTR gene, which results in cystic fibrosis.
- A single substitution in which valine is utilized instead of glutamic acid results in sickle cell anemia.

4.

What Does Point vs. Deletion Mutation Mean?

Point mutations also include insertions and deletions. An insertion is when base pairs are added to a DNA sequence, and an omission is when base pairs are removed from a DNA sequence. A deletion mutation happens when a base pair is deleted from a sequence. 

5.

What Exactly Are Frame Mutation and Point Mutation?

A point mutation is a genetic change induced by substituting a single nucleotide for another. Frameshift mutations occur when a base is added or removed from the nucleotide sequence, causing a shift in the reading frame.

6.

Which Disease Is Caused by a Point Mutation?

Point mutations are the most common cause of blood disorders such as ß-thalassemia, sickle cell disease, hereditary spherocytosis, Fanconi anemia, and Haemophilia A and B.

7.

Who Proposed the Concept of Point Mutation?

Ernst Freese invented the word "transitions" or "transversions" in 1959 to classify various forms of point mutations. Transitions involve substituting a pyrimidine base with another pyrimidine or a purine base with another purine. A purine is converted into a pyrimidine during a transversion.

8.

What Three Consequences Do Point Mutations Have?

A point mutation is referred to as a point mutation when one base pair is added, removed, or modified in a genome. Most point mutations are safe, but they can also have a variety of functional impacts, like alterations to encoded proteins or changes in gene expression.

9.

What Is Point or Substitution Mutation?

Substitution mutation refers to one nucleotide that may be substituted for a different nucleotide. Furthermore, this term can be employed to describe the replacement of one amino acid with another within a protein.

10.

What Distinguishes Frameshift From a Point Mutation?

1. Point Mutation:
- A point mutation in a gene is one in which a base pair is changed, deleted, or added. 
- Transitions and changes characterize it. 
- The gene's structure varies as a result of this.
- It causes disorders such as sickle cell anemia.
2. Frameshift mutation:
- Frameshift mutations arise when a nucleotide is added or deleted from the DNA sequence, disrupting the reading frame.
- It involves insertion and deletion. 
- It results in a change in the number of nucleotides.
- It causes diseases like cystic fibrosis and Crohn's disease.

11.

Why Is Sickle-Cell Anemia Referred to as a Point Mutation?

A single nucleotide alteration causes sickle-cell anemia, and it is only one type of point mutation. Chromosome-level modifications to the DNA sequence can also occur when substantial portions of chromosomes change. As a result, it is known as a point mutation.

12.

What Kind of Point Mutation Is the Very First One?

The first kind of point mutation is a transition mutation. Transition mutations happen when a purine base such as adenine (A) or guanine (G) replaces another purine base or when a pyrimidine base such as thymine (T) or cytosine (C) replaces another pyrimidine base.

13.

What Kind of Point Mutation Is the Most Dangerous?

A frameshift mutation is the most dangerous point mutation for cells or organisms. Adding or removing nucleotide sequences that cause frameshift mutation is more harmful. It alters the amino acid sequences of a polypeptide chain.

14.

What Distinguishes Polymorphism From a Point Mutation?

A point mutation occurs when a single base pair in the nucleotide sequence of a gene changes. A change affecting more than one percent of a specific group is called polymorphism.

15.

What Benefits Do Point Mutations Offer?

Beneficial mutations, which are inherited, improve the likelihood that an organism will survive and be naturally selected are few advantages of mutations. Mutations have enabled humans to adapt to their surroundings. It also increases the diversity of the population.

16.

What Type of Point Mutation Is Most Typical?

There are two common types of point mutations include:
- Transition Mutation: A transition mutation is a type of point mutation where a nucleotide is replaced by another nucleotide of the same chemical category, either another purine substitutes a purine (adenine or guanine), or another pyrimidine substitutes a pyrimidine (cytosine or thymine).
- Transversion Mutation: A transversion mutation is a point mutation where a nucleotide of a different chemical category replaces a nucleotide. Either a pyrimidine or a pyrimidine substitutes a purine is substituted by a purine.
Source Article IclonSourcesSource Article Arrow
Dr. Vishal Patidar
Dr. Vishal Patidar

General Medicine

Tags:

genetic disorderpoint mutationcystic fibrosis
Community Banner Mobile
By subscribing, I agree to iCliniq's Terms & Privacy Policy.

Source Article ArrowMost popular articles

Do you have a question on

cystic fibrosis

Ask a doctor online

*guaranteed answer within 4 hours

Disclaimer: No content published on this website is intended to be a substitute for professional medical diagnosis, advice or treatment by a trained physician. Seek advice from your physician or other qualified healthcare providers with questions you may have regarding your symptoms and medical condition for a complete medical diagnosis. Do not delay or disregard seeking professional medical advice because of something you have read on this website. Read our Editorial Process to know how we create content for health articles and queries.

This website uses cookies to ensure you get the best experience on our website. iCliniq privacy policy