Difference Between Robertsonian and Reciprocal Translocation

The key difference between Robertsonian and reciprocal translocation is that Robertsonian translocation refers to the exchange of genetic material between five acrocentric chromosome pairs, which causes the reduction of usual chromosome number in a cell, while reciprocal translocation refers to the exchange of genetic material between non homologous chromosomes, which do not cause a change in chromosome number.

Genetic translocation is the event of exchanging genetic material between chromosomes. Due to translocation, genetic materials rearrange between chromosomes. Some translocations do not result in a gain or a loss. In simple words, genetic materials exchange occurs without extra or missing genetic material. They are balanced translocations. In contrast, unbalanced translocations cause unequal exchange of genetic material, leading to trisomy or monosomy of a particular chromosome segment. Hence, it results in missing or extra genes in chromosomes.

CONTENTS

1. Overview and Key Difference
2. What is Robertsonian Translocation
3. What is Reciprocal Translocation
4. Similarities Between Robertsonian and Reciprocal Translocation
5. Side by Side Comparison – Robertsonian vs Reciprocal Translocation in Tabular Form
6. Summary

What is Robertsonian Translocation?

Robertsonian translocation is a type of chromosomal abnormality that occurs due to the exchange of chromosome segments between acrocentric chromosomes. Thus, this kind of chromosomal abnormality commonly takes place in acrocentric chromosome pairs numbered 13, 14, 15, 21 and 22. In this type, a certain chromosome remains attached to another one. They are cytologically visible and can reduce chromosome number when the short arms are lost due to the fusion of long arms of two acrocentric chromosomes. Therefore, most people with Robertsonian translocation have only 45 chromosomes in each of their cells.

Figure 01: Robertsonian Translocation

Carrier of Robertsonian translocation is healthy. But, problems may arise in their children. Down syndrome and Patau syndrome are two such cases that occur in children due to Robertsonian translocation. In addition to these syndromes, Robertsonian translocations may also result in infertility problems, stillbirth and miscarriages.

What is Reciprocal Translocation?

Reciprocal translocation is the exchange or swapping of chromosome segments between nonhomologous chromosomes. In reciprocal translocation, the exchange of chromosome segments especially occurs between two chromosomes that do not belong to the same pair of chromosomes. For example, a specific reciprocal translocation takes place between chromosomes 1 and 19. Since the chromosome material exchange between two non-homologous chromosomes, two translocated chromosomes are generated. Furthermore, the places of centromere and the sizes of chromosomes may vary greatly due to reciprocal translocation.

Figure 02: Reciprocal Translocation

In balanced reciprocal translocation, there is no apparent loss of genetic material. Therefore, reciprocal translocations do not normally cause diseases. However, it may cause infertility problems and miscarriages.

What are the Similarities Between Robertsonian and Reciprocal Translocation?

• Both Robertsonian and reciprocal translocations are chromosomal abnormalities.
• They occur as a result of exchanging genetic material between chromosomes.
• Both cause miscarriages, infertility problems, etc.

What is the Difference Between Robertsonian and Reciprocal Translocation?

Robertsonian translocation occurs in acrocentric chromosomes and leads to the reduction of chromosome number. In contrast, reciprocal translocation occurs in nonhomologous chromosomes, and it does not cause a reduction in chromosome number. So, this is the key difference between Robertsonian and reciprocal translocation. Furthermore, the reciprocal translocation is more common than Robertsonian translocation.

Below infographics shows more comparisons related to the difference between Robertsonian and reciprocal translocation.

Summary – Robertsonian vs Reciprocal Translocation

Robertsonian translocation and reciprocal translocation are two common chromosomal translocations. Robertsonian translocation occurs in acrocentric chromosome pairs. Here, genetic materials exchange between acrocentric chromosomes, leading to loss of short arms and fusing the long arms together. In reciprocal translocation, chromosome fragments exchange or swap between nonhomologous chromosomes generating two translocated chromosomes. Thus, there is no apparent genetic material loss in reciprocal translocation. So, this concludes the summary of the difference between Robertsonian and reciprocal translocation.

Reference:

1. Griffiths, Anthony JF. “Translocations.” An Introduction to Genetic Analysis. 7th Edition., U.S. National Library of Medicine, 1 Jan. 1970, Available here.
2. “Chromosomal Translocation.” Wikipedia, Wikimedia Foundation, 26 June 2019, Available here.

Image Courtesy:

1. “Translocacion robertsoniana” By UPO649 1112 mreycor1 – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “Translocation-4-20” By National Human Genome Research Institute – (Public Domain) via Commons Wikimedia

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