Difference Between Point Mutation and Chromosomal Mutation

The key difference between point mutation and chromosomal mutation is that point mutation is a small scale mutation in which a single base pair of the DNA or RNA sequence changes while chromosomal mutation is a large scale mutation in which the structure of the chromosome changes.

A mutation is an alteration or a change in the nucleotide sequence of DNA or RNA. Mutations are the main cause of genetic variability among the organisms. Mutations occur in somatic cells as well as in germ line cells. Some mutations are inherited by the next generation while others are non-inheritable. Somatic mutations affect the present organism while germline mutations transmit to the next generation. Point mutation and chromosomal mutation are two common types of mutations. Point mutations are the simplest type of mutations that arise due to a single base pair change. On the other hand, chromosomal mutations are somewhat large scale changes in which the structure or number of chromosomes change in an organism.

CONTENTS

1. Overview and Key Difference
2. What is a Point Mutation 
3. What is a Chromosomal Mutation
4. Similarities Between Point Mutation and Chromosomal Mutation
5. Side by Side Comparison – Point Mutation vs Chromosomal Mutation in Tabular Form
6. Summary

What is a Point Mutation?

Point mutation is an alteration in a single nucleotide in a DNA or RNA sequence. It can happen due to changing, inserting or deleting a single base pair in the nucleic acid. Most point mutations occur due to the errors in the DNA replication process. Furthermore, point mutations can also take place due to some other reasons such as exposure to UV or X rays, and carcinogenic chemicals.

There are two types of point mutations as transition mutations and transversion mutations. During transition mutation, a pyrimidine base is substituted for another pyrimidine base or a purine base is substituted for another purine base. During transversion mutation, a purine base is substituted for a pyrimidine base or vice versa.

In addition, based on the effect of the final product, point mutations can be further grouped as silent mutations, missense mutations, and nonsense mutations. Silent mutations result in functionally same amino acids at the end while missense mutations result in functionally different amino acids. Thus, the resultant protein in missense mutation may show alteration or loss of function accordingly. Nonsense mutations cause premature protein synthesis which leads to the complete loss of protein function. Point mutations can cause several diseases including cystic fibrosis, sickle cell anemia, Tay-Sachs disease, etc.

What is a Chromosomal Mutation?

A chromosomal mutation is a type of large scale mutation. It changes the structure of a chromosome or the total number of chromosomes in a chromosome set. Further, this kind of mutation occurs due to duplication, translocation, inversions, or deletion of a part of the chromosome and also due to errors in cell division processes such as crossing over, and non-disjunction.

Chromosomal mutations can cause gene imbalance as well as unmasking of deleterious alleles in other chromosomes. Hence, the impact of chromosomal mutation is high when comparing to point mutation. Since chromosomal mutations occur in a part of a chromosome, it can include many genes. Hence, the magnitude of the impact of chromosomal mutation is extremely high. Klinefelter syndrome, Turner syndrome, and Down syndrome are several syndromes that occur due to chromosomal mutations.

What are the Similarities Between Point Mutation and Chromosomal Mutation?

• Point mutation and chromosomal mutation are two types of genetic mutations occurring in living organisms.
• In both cases, the nucleotide sequences are altered.
• Thus, both types of mutations can cause lethal diseases.

What is the Difference Between Point Mutation and Chromosomal Mutation?

Point mutation is a single nucleotide change that occurs in a DNA or RNA sequence while chromosomal mutation is a structural or numerical change in chromosomes. Thus, this is the key difference between point mutation and chromosomal mutation. In point mutation, changes occur in a single base pair. But in chromosomal mutation, changes occur in a part of a chromosome or the total number of chromosomes in a chromosome set. Therefore, this is also a significant difference between point mutation and chromosomal mutation.

Moreover, a further difference between point mutation and chromosomal mutation is the impact of the mutation. The impact of a point mutation is comparatively low while it is high in chromosomal mutation. Also, the point mutations are caused due to insertions, deletions, changes, etc, while chromosomal mutations are caused due to duplication, translocation, inversions, deletion, non-disjunction of chromosomes, crossing over, etc. Therefore, this is a major difference between point mutation and chromosomal mutation. Sickle cell anemia, hemophilia, cystic fibrosis, Huntington syndrome, Tay-Sachs disease, and cancers are some of the diseases that occur due to point mutations. On the other hand, Klinefelter syndrome, Turner syndrome, and Down syndrome are some syndromes that occur due to chromosomal mutations.

Summary – Point Mutation vs Chromosomal Mutation

Point mutation refers to a single base pair alteration in a DNA or RNA sequence. It is a small scale mutation. Whereas, chromosomal mutation refers to a structural or numerical change in chromosomes of an organism. It is a large scale mutation. The impact of chromosomal mutation is high since the altered segment of a chromosome may include several or many genes. Point mutations occur due to change, insertion, or deletion. On the other hand, chromosomal mutation may occur due to duplication, translocation, inversions, deletion, non-disjunction of chromosomes, crossing over, etc. Thus, this is the summary of the difference between point mutation and chromosomal mutation.

Reference:

1. “Point Mutation.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., 4 Feb. 2014, Available here.
2. “Genetic Mutation.” Nature News, Nature Publishing Group, Available here.

Image Courtesy:

1. “Point mutations-en” By Jonsta247 – Own work (CC BY-SA 4.0) via Commons Wikimedia
2. “Chromosomes mutations-en” By GYassineMrabetTalk✉This W3C-unspecified vector image was created with Inkscape. – Own work based on Chromosomenmutationen.png (Public Domain) via Commons Wikimedia