Difference Between Inversion and Translocation

Main Difference – Inversion vs Translocation

A mutation is a change in the nucleotide sequence of the genome. Mutations may arise due to the errors of DNA replication or damaging effect of mutagens. They can be classified based on their effect on the DNA molecule. Point mutations, frameshift mutations, and chromosomal mutation are the three main types of mutation that occur in the genome. Inversion and translocation are two types of chromosomal mutations. Both inversion and translocation are alterations of chromosomal segments. The main difference between inversion and translocation is that inversion is the change in the orientation of a segment of chromosome whereas translocation is the interchange of the parts of chromosomes between nonhomologous chromosomes.

Key Areas Covered

1. What is an Inversion
     – Definition, Types, Effect
2. What is a Translocation
     – Definition, Process, Effect
3. What are the Similarities Between Inversion and Translocation
     – Outline of Common Features
4. What is the Difference Between Inversion and Translocation
     – Comparison of Key Differences

Key Terms: Centromere, Chromosomal Mutation, Chromosomes, Homozygosity, Paracentric Inversion, Pericentric Inversion, Reciprocal Translocation, Translocation 

What is an Inversion

An inversion is a rearrangement in which an internal chromosome segment is broken down at two different locations, flipped 180 degrees to rejoin. The two types of inversions can be identified in relation to the location of the centromere. They are the paracentric inversion and pericentric inversion. In paracentric inversion, the centromere of the chromosome is located outside the inversion. In pericentric inversion, the centromere occurs within the inverting region. A paracentric inversion is shown in figure 1.

Figure 1: Paracentric Inversion

However, inversions do not change the overall amount of genetic material. Therefore, they do not exhibit abnormalities in the phenotypic level. But, if one of the breakpoints of the inversion is located within a gene of an essential function, that breakpoint serves as a lethal gene mutation. In such cases, the mutated chromosome losses its homozygosity. However, most inversions do not disturb the homozygosity of the chromosomes.

What is a Translocation

A translocation refers to a rearrangement in which acentric segments exchange between two nonhomologous chromosomes. It is also called a reciprocal translocation. Typically, translocation changes the size of the chromosome as well as the position of the centromere. A translocation is shown in figure 2.

Figure 2: Translocation

Translocation also does not change the amount of genetic material in the genome. But, chromosomal disorders may occur due to the loss of homozygosity of chromosomes. Some translocations in plants may considerably reduce the yield. On the other hand, the introduction of translocations into insect pest’s genomes can be used as a control mechanism for them.

Similarities Between Inversion and Translocation

• Inversion and translocation are two types of chromosomal mutations caused by mutagens.
• Both inversion and translocation are caused by the breakage of DNA double helices at two different locations of the genome, followed by the rejoining of the broken ends, producing a new chromosomal arrangement of genes.
• Both inversion and translocation alter the segment of chromosomes.
• Both inversion and translocation do not change the amount of genetic material in the genome.
• Both inversion and translocation may change the position of the centromere.
• Both inversion and translocation lead to the loss of homozygosity of chromosomes, reducing the opportunity for crossing-over during meiosis.

Difference Between Inversion and Translocation

Definition

Inversion: An inversion refers to a rearrangement in which an internal chromosome segment is broken down at two different locations, flipped 180 degrees to rejoin.

Translocation: A translocation refers to a rearrangement in which acentric segments are exchanged between two nonhomologous chromosomes.

Significance

Inversion: Inversion is a change in the orientation of a segment of a chromosome.

Translocation: Translocation is the interchange of the parts of chromosomes between nonhomologous chromosomes.

Number of Chromosomes

Inversion: Inversion is a single chromosome mutation.

Translocation: Two chromosomes are involved in the translocation.

Size of the Chromosome

Inversion: The size of the chromosome does not change in inversions.

Translocation: The size of the chromosome changes in translocation.

Abnormalities

Inversion: Typically, inversion does not cause abnormalities.

Translocation: Translocations more likely to cause a disease such as infertility, cancer or Down syndrome.

Conclusion

Inversion and translocation are two types of chromosomal mutations that occur in the genome. Both types of mutations do not change the amount of genetic material in the genome. Inversion is the breakdown and rejoining of a segment of a chromosome while translocation is the exchange of chromosome segments between nonhomologous chromosomes. The main difference between inversion and translocation is the mutating mechanism.

Reference:

1. “Single Chromosome Mutations” By Zephyris at the English language Wikipedia (CC BY-SA 3.0) via Commons Wikimedia
2. “Figure 13 03 09” By CNX OpenStax – (CC BY 4.0) via Commons Wikimedia