The key difference between deletion and duplication of chromosome is that deletion of chromosome results in the loss of genetic material while duplication of chromosome results in the gain of extra copies of genetic material.
Chromosomes carry the genetic material of an organism. They are thread-like structures composed of DNA. They consist of nucleotide sequences. Changes or rearrangements can happen to the structure of the chromosomes due to various reasons. These changes can cause problems in growth, development, function and survival of an organism. Genes are parts of the chromosomes. Structural changes in chromosomes affect genes and their expression (making proteins). Some chromosomal changes affect a person’s health, but some changes do not. The effect of the chromosomal change depends on the size and location, and whether any genetic material is gained or lost. The major types of chromosomal rearrangements are translocation, deletion, duplication and inversions.
CONTENTS
1. Overview and Key Difference
2. What is Deletion of Chromosome
3. What is Duplication of Chromosome
4. Similarities Between Deletion and Duplication of Chromosome
5. Side by Side Comparison – Deletion vs Duplication of Chromosome in Tabular Form
6. Summary
What is Deletion of Chromosome?
Deletion of chromosome is a type of chromosome rearrangement. It is simply the loss of a part of the chromosome arm. Chromosomes can break from two different locations. Generally, the broken arm does not have a centromere. Hence, it does not reattach to the chromosome and is lost. As a result, a part of the genetic material is lost from the genome of an organism. The effect of deletion depends on the size of the segment lost. Even a small deletion within a gene inactivates the gene.
Figure 01: Deletion of Chromosome
In the human genome, specific deletions of chromosomes cause unique syndromes. The cri du chat syndrome is one such syndrome caused by a heterozygous deletion of the tip of the short arm of chromosome 5. This syndrome is identified by the distinctive catlike mewing cries made by infants. Mental retardation, microencephaly (abnormally small head) and a moonlike face are the other phenotypic manifestations of the syndrome. Prader-Willi syndrome (PWS) is another syndrome which occurs due to a deletion on the long arm of chromosome 15. PWS is also associated with mental retardation and physical defects.
What is Duplication of Chromosome?
Duplication of chromosome is another type of chromosomal rearrangement. Duplication of chromosome occurs when a fragment of DNA detaches from a chromosome and re-attaches into a homologous chromosome. As a result, an extra copy of some chromosome region is produced in the homologous chromosome. The genes in that particular region have a different copy number. Since the gene dosage is different, it can affect the phenotype. Extra genes can synthesize excess proteins, leading to developmental defects.
Figure 02: Duplication of Chromosome
In humans, compared to defects caused by deletions, the severity of the genetic defects is low in duplications. Charcot-Marie-Tooth disease type I is a genetic disease caused by chromosomal duplication. Furthermore, Pallister Killian syndrome is another syndrome where a part of chromosome number 12 is duplicated. Drosophila Bar eye mutation is also a defect caused by duplication.
What are the Similarities Between Deletion and Duplication of Chromosome?
- Deletion and duplication are two major types of chromosomal rearrangements.
- Both deletion and duplication are imbalanced rearrangements.
- In both types, the detached segment of DNA fails to reattach with the same chromosome.
- A too-large segment of DNA cannot be deleted or duplicated.
- The rules governing gene balance apply for deletion or duplication of chromosomes.
- The larger the segment of a chromosome deleted or duplicated, the more likely it is to cause phenotypic abnormalities.
- Deletions and duplications can be produced by illegitimate crossing over.
- They mostly occur during cell division when chromosomes align.
What is the Difference Between Deletion and Duplication of Chromosome?
Deletion of chromosomes causes the loss of parts of chromosomes while duplication of chromosomes results in an extra copy of some chromosome region. So, this is the key difference between deletion and duplication of chromosome. Moreover, deletion occurs when a detached fragment fails to reattach to the same chromosome while duplication occurs when the detached fragment reattaches to a homologous chromosome.
The below infographic tabulates more differences between deletion and duplication of chromosome.
Summary – Deletion vs Duplication of Chromosome
Chromosomal rearrangements can happen due to deletions or duplications. In chromosomal deletion, a fragment of DNA detaches from the chromosomes and fails to reattach to the same chromosome. Hence, the detached segment is lost. In chromosomal duplication, a fragment of DNA detaches from a chromosome and attaches to the homologous chromosome. Both deletion and duplication of chromosomes are imbalanced chromosomal rearrangements. Thus, this summarizes the difference between deletion and duplication of chromosome.
Reference:
1. Griffiths, Anthony JF. “Chromosomal Rearrangements.” Modern Genetic Analysis., U.S. National Library of Medicine, 1 Jan. 1999, Available here.
2. “DNA Deletion and Duplication and the Associated Genetic Disorders.” Nature News, Nature Publishing Group, Available here.
Image Courtesy:
1. “22 del q11.2” By genetics4medics – (CC BY-SA 4.0) via Commons Wikimedia
2. “Gene-duplication” By National Human Genome Research Institute – (Public Domain) via Commons Wikimedia
