Translocation (Chromosome Mutation) — Definition & Impact

Illustrated · 1 min

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Swapping Genetic Information

Translocation is when a piece of one chromosome is swapped with a piece from another chromosome. The two chromosomes are not homologous; they have to be different chromosomes. This swapping happens because the two chromosomes have similar segments that enable them to cross over during meiosis. This type of mutation does not change the amount of genetic information available.

The image shows an example of reciprocal translocation.
There are two chromosomes side by side. One is orange and one is teal. The bottom part of each chromosome is surrounded by a box. In the second half of the picture, the selected areas has switched with each other. The resulting chromosomes are orange with a teal end, and teal with an orange end.
Image text reads: "There is no change in the amount of genetic information." — Image source: By Mario Janakis

What Kinds Are There?

There are a few types of chromosomal translocations:

Reciprocal translocation is when two parts of two chromosomes switch places.

If it is balanced, an equal portion of chromosome material has been swapped. If it is unbalanced, there is an unequal sharing between chromosomes. This could result in one chromosome being longer or shorter than it is supposed to be.

A Robertsonian translocation is when someone has 45 chromosomes instead of the usual 46. This happens when two chromosomes get stuck together, forming one long chromosome.

The image shows a Robertsonian translocation. The first half of the image shows one orange chromosome and one teal chromosome side by side. It is labeled "Before translocation". A box surrounds the bottom half of the teal chromosome and an arrow is pointing to the top of the orange chromosome.
The second half of the image shows that the bottom of the teal chromosome has fused with the bottom of the orange chromosome, resulting in one long chromosome.
Image text reads: "The two chromosomes stick together, resulting in 35 rather than 36 chromosomes." — Image source: By Mario Janakis

When Do These Mutations Occur?

Chromosomal mutations all happen during meiosis. Chromosomes in meiosis have the opportunity to line up and crossover. 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, and translocation) will go unnoticed in the sperm or egg. When a mutated egg or sperm becomes fertilized, the mutations that occurred in the parent's cells become noticeable.

Video

By Mario Janakis

(Video) Reciprocal Translocation

by UCD Medicine

Reciprocal translocations occur when two chromosomes swap parts with each other. This can be either a balanced sharing or an unbalanced sharing. Offspring can still be healthy if a parent carries a balanced translocation. However, if they carry a translocation that is unbalanced, it could result in birth defects or miscarriage. Since outcomes vary based on family history, genetic testing is necessary to determine individual risk.

(Video) Robertsonian Translocation

by UCD Medicine

A Robertsonian translocation occurs when two chromosomes stick together. This happens with acrocentric chromosomes, which are numbers 13, 14, 15, 21, and 22.

Robertsonian translocation carriers are healthy, but they pose a risk for offspring. If the translocated chromosome is passed on along with a standard chromosome, it can result in three copies of that chromosome (called a trisomy) being present. This chromosomal abnormality can have a wide range of effects, including causing Down Syndrome.

Illustrated · 1 min

By Samantha Broders

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