Inversion (Chromosome Mutation) — Definition & Examples

What Does Inversion Mean?

Chromosome mutations change the number or structure of the chromosomes. These mutations can even change the location and number of certain genes on a chromosome. These mutations can happen because of both internal and external influences, like during meiosis or exposure to radiation. Mutations occur most often during the crossing-over stage of meiosis when homologous chromosomes trade pieces of each other.

Inversion occurs when a part of the chromosome breaks off, flips around, and becomes reattached. So, the order of the genes becomes reversed from what it was. A trick to remember this is that inverse sounds like reverse.

Although inversions often don't have any observable effect on the carrier, they can lead to an increased risk of abnormal offspring.

What Kinds Are There?

Pericentric Inversions

First, let's break down the word. Peri means "around" and centric means "center". So, pericentric inversions happen when the centromere is included in the break. In other words, the break happens in the center of the chromosome.

Paracentric Inversions

On the other hand, paracentric inversions (para meaning "beside") occur when a chromosome breaks in one of its arms. In other words, the centromere is not included.

$$\color{#8925AE}{\text{Vocabulary Review:}}$$

$\color{#8925AE}{\text{Chromosome Mutation}}$ : Changes that affect the number or structure of the chromosomes. They can even change the location and number of certain genes on a chromosome

$\color{#8925AE}{\text{Inversion}}$ : Mutation that happens when a part of the chromosome breaks off, flips around, and becomes reattached

$\color{#8925AE}{\text{Duplication}}$ : Duplication happens when a chromosome has extra copies of a gene

$\color{#8925AE}{\text{Translocation}}$ : Translocation happens when a part of the chromosome breaks off and attaches to another chromosome

$\color{#8925AE}{\text{Deletion}}$ : A mutation that occurs when part of the chromosome is deleted

$\color{#8925AE}{\text{Meiosis}}$ : The process of dividing one nucleus into four unique haploid cells. Only occurs in sex cells

$\color{#8925AE}{\text{Chromosome}}$ : A chromosome is a long, single, coiled piece of DNA

What Is Inversion?

Inversion is a type of chromosome rearrangement where a segment of a chromosome gets flipped around. These mutations aren't totally awful because there is still the same amount of genetic material.

Chromosomal mutations all happen during meiosis. Chromosomes in meiosis have the opportunity to line up and cross over. This mixes up the genetic information from the parents in the sperm or egg. However, during crossing over things can go wrong. All of these chromosomal mutations (deletion, inversion, duplication, translocation) will go unnoticed in the sperm or egg. When a mutated egg or sperm becomes fertilized, the mutations that occurred in the parents' cells become noticeable.

(Video) Chromosomal Mutations

by Kevin Glass

A chromosomal inversion is when a piece of a chromosome breaks off, flips around, and reattaches. Watch the video above to see what this actually looks like.