Genetic Review: What is the Difference Between Gene Mutations and Chromosomal Mutations?

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Overview of Genes and Chromosomes

Before we start to learn what is the difference between gene mutation and chorosomal mutation, it is often easier to know first a few facts about genes and chromosomes and their specific functions.

Most cells in the human body contains a nucleus, and in the nucleus are very tiny threadlike units called chromosomes. There are a total of 46 chromosomes in each individual. Twenty-three of them came from the mother and 23 came from the father. Of the 23 pairs, one pair is composed of the sex chromosomes which determines the gender of a person, and the other 22 pairs are called autosomes, which determines other characteristics, like eye color and height, among many other characteristics.

These chromosomes are made up of thousands of genes. A gene contains a sequence of DNA that carries information or instructions on how to make specific proteins inside the body. Proteins are important building blocks for muscles, teeth, blood and all the other organs, and they are necessary in the proper development and functioning of the human body.

What is the Difference Between Gene Mutations and Chromosomal Mutations?

Mutations are some changes or alterations that occur in the sequence of DNA. They are often caused by exposure to radiation, viruses and chemicals. Some mutations may occur in a random manner during cell division. The result of mutations are varied, some may not be apparent, while others may manifest as disease processes.

Genetic mutations can either be acquired or inherited. Inherited gene mutations are passed from affected parents to their children. Somatic or acquired mutation is the alteration in the DNA sequence of the gene that is brought after exposure to certain environmental factors like radiation.Gene mutation usually occurs in two different ways, namely, base substitution and frame shifts. Base substitution involves replacing one base pair and its complementary partner, while frame shifts develop when there is one or several bases involved. Examples of gene mutations include Marfan syndrome, cystic fibrosis and sickle cell disease.

Chromosome mutation occurs when there are changes in the number or structure of the chromosomes. The mutation in relation to numbers typically occurs by the time the zygote is forming or developing inside the womb. These changes in chromosome structure are frequently caused by inversion, insertion, duplication or deletion of a chromosomal segment. Inversion takes place when there is reversal in the chromosome’s segment. Insertion or translocation occurs when a piece of chromosome attaches itself to a non-homologous chromosome. Duplication happens when an extra chromosome appears, while deletion takes place when there is deficiency in the portion of the DNA. The most common chromosomal birth defect is the Trisomy 21 or Down’s syndrome where the chromosome 21 of the person has an extra copy.


Genetics Home Reference: What is a gene mutation and how do mutations occur?

Evolution Basic Tour: Chromosome Mutation