The key difference between aneuploidy and polyploidy is that the aneuploidy is a condition that happens due to a missing or an extra chromosome in the genome of an organism while the polyploidy is a condition when a cell contains more than two sets of chromosomes.
Every organism has a particular set of chromosomes in each cell, and it is constant to an organism. In human, there are 23 homologous chromosome pairs. Out of them, 22 are autosomes while one pair is allosomes and involves in sex determination. Accordingly, diploid refers to organisms that have two sets of homologous chromosomes. Most of the species are diploid and symbolized as 2n organisms. In higher plants, the sporophyte is diploid. Humans are also diploid.
On the other hand, haploid organisms have one set of chromosomes, and their symbol is n. Other than 2n and n, some organisms have more than two sets of chromosomes and are called polyploidy. Most of the plant species show polyploidity, but rare in higher animals. In contrast, Aneuploidy is a condition, which has a missing chromosome or adding a particular chromosome or part of a chromosome. Both polyploidy and aneuploidy show the abnormality of the chromosome number.
CONTENTS
1. Overview and Key Difference
2. What is Aneuploidy
3. What is Polyploidy
4. Similarities Between Aneuploidy and Polyploidy
5. Side by Side Comparison – Aneuploidy vs Polyploidy in Tabular Form
6. Summary
What is Aneuploidy?
Aneuploidy is a condition where an abnormal number of chromosomes are present in the genome. Generally, aneuploidy occurs when one chromosome is missing or having one extra chromosome. Due to that, the total number of chromosomes in a cell differs from the wild type of the organism. According to the difference of the number of the chromosome, there are several types of aneuploidy such as monosomy (2n-1), disomy (n+1), trisomy (2n+1) and nullisomy (2n-2) where the parent phenotype is 2n.
Figure 01: Aneuploidy – Klinefelter Syndrome
Aneuploidy occurs mainly due to the failure of segregating chromosomes properly to the opposite poles in nuclear division. That is; in mitosis or meiosis, both sister chromatids or homologous chromosomes go to one pole, or in other words, none to other. Moreover, genetic disorders such as Down syndrome, Klinefelter syndrome and Turner syndrome are due to aneuploidy conditions.
What is Polyploidy?
Polyploidy is a condition when a cell contains more than two sets of chromosomes. So it alters the chromosome number in a cell. Polyploidy can be seen frequently in flowering plants including important crop plants but rarely in animals, except vertebrates and invertebrates. Several types of polyploidy occur through several processes. Autopolyploidy is one type that results due to the multiplication of the genome of same species. It is produced during the gamete formation in sexual reproduction when meiosis occurs.
Figure 02: Polyploidy
Furthermore, autoplidy can occur due to the abnormal cell division in mitosis. Allopolyploidy is another type of polyploidy condition that occurs due to the combination of genomes of different species such as in hybrid species. Polyploidy also can be induced using various chemicals such as colchicine by inhibiting cell division.
What are the Similarities Between Aneuploidy and Polyploidy?
- Aneuploidy and polyploidy are two types of conditions that create an abnormal number of chromosomes in the genome of the cells.
- Both conditions create lethal genetic diseases.
- Also, both disrupt the existing equilibrium in cells.
- And, both occur due to nondisjunction in meiosis or mitosis.
What is the Difference Between Aneuploidy and Polyploidy?
The key difference between aneuploidy and polyploidy is that aneuploidy occurs due to altering particular chromosome or part of a chromosome such as 2n-1(monosomic), etc., while polyploidy occurs due to altering a set of chromosome number such as 2n, 3n, 5n, etc. Furthermore, aneuploidy can be seen in human as genetic disorders; for example, Turner syndrome and Down syndrome, whereas polyploidy can be seen in some human muscle tissues. Aneuploidy is more common in human, whereas polyploidy is rare in human. Thus, it is another difference between aneuploidy and polyploidy.
Concerning plants too, we can identify a difference between aneuploidy and polyploidy; polyploidy can be seen in plants more common than aneuploidy. Below is an infographic on the difference between aneuploidy and polyploidy.
Summary – Aneuploidy vs Polyploidy
Aneuploidy and polyploidy are two chromosomal abnormalities that occur in plants and animals. Aneuploidy is a condition which changes the total number of chromosomes in a cell. Generally, it occurs when there is an extra chromosome present or when there is a missing chromosome. On the other hand, polyploidy is a condition that refers to having more than two sets of chromosomes. Hence the ploidy of the organism changes from 2n to 3n, 4n, etc. Aneuploidy is very common in humans while polyploidy is very common in plants. Thus, this is the difference between aneuploidy and polyploidy.
Reference:
1. Griffiths, Anthony JF. “Aneuploidy.” Current Neurology and Neuroscience Reports., U.S. National Library of Medicine, 1 Jan. 1970. Available here
2. Nature News, Nature Publishing Group. Available here
Image Courtesy:
1.”Human chromosomesXXY01″By Nami-ja – Own work, (Public Domain) via Commons Wikimedia
2.”Figure 18 02 07″By CNX OpenStax (CC BY 4.0) via Commons Wikimedia