Difference Between Symmetric and Asymmetric Karyotype

The key difference between symmetric and asymmetric karyotype is that symmetric karyotype shows a smaller difference between the smallest and largest chromosomes in the set while asymmetric karyotype shows a larger difference between the smallest and largest chromosomes in the set.

A karyotype is a diagram which shows the correct number and structure of the complete set of chromosomes in the nucleus of the eukaryotic cell. Karyotyping is a technique performed by doctors to examine the complete set of the chromosomes in the nucleus. Chromosomes are visible only during the metaphase of cell division. Karyotypes reveal structural features of each chromosome. Moreover, karyotypes are useful in studying chromosome banding patterns. In addition, karyotypes help in the identification of chromosomal aberrations. Not only that, karyotypes are extremely helpful in diagnosing prenatal genetic defects. There are two types of karyotypes as symmetric and asymmetric karyotype. A symmetric karyotype has more metacentric chromosomes while an asymmetric karyotype has more acrocentric chromosomes.

1. Overview and Key Difference
2. What is a Symmetric Karyotype
3. What is an Asymmetric Karyotype
4. Similarities Between Symmetric and Asymmetric Karyotype
5. Side by Side Comparison – Symmetric vs Asymmetric Karyotype in Tabular Form
6. Summary

What is a Symmetric Karyotype?

A symmetric karyotype is a karyotype which shows a smaller difference between the smallest and largest chromosomes in the set. It consists of more metacentric chromosomes. All the chromosomes are approximately the same size. Moreover, they have media or sub-mediam centromeres. Symmetric karyotype is not considered as an advanced feature compared to asymmetric karyotype. In fact, it represents a primitive state.

Difference Between Symmetric and Asymmetric Karyotype

Figure 01: Female Karyotype

What is an Asymmetric Karyotype?

Asymmetric karyotype is a karyotype which shows a larger difference between the smallest and largest chromosomes of the set. It has a fewer metacentric chromosomes. Most of the chromosomes are acrocentric. Asymmetric karyotype is considered to be a relatively advanced feature. It has evolved through structural chromosome changes. In flowering plants, scientists have observed a predominant trend towards the asymmetric karyotype. Moreover, an increased asymmetric karyotype is associated with specialized zygomorphic flowers. Ginkgo biloba also has asymmetric karyotype.

What are the Similarities Between Symmetric and Asymmetric Karyotype?

Symmetric and asymmetric karyotype are the two types of karyotypes based on the difference between the smallest and largest chromosomes in the set.
The concept of symmetrical or asymmetrical was developed by Levitzky in 1931.

What is the Difference Between Symmetric and Asymmetric Karyotype?

A symmetric karyotype is a karyotype showing a small difference between the smallest and largest chromosomes in the set. Meanwhile, an asymmetric karyotype is a karyotype showing a large difference between the smallest and largest chromosomes of the set. So, this is the key difference between symmetric and asymmetric karyotype. Furthermore, symmetric karyotype has more metacentric chromosomes while asymmetric karyotype has few metacentric chromosomes. But, it has more acrocentric chromosomes.

The below infographic tabulates more differences between symmetric and asymmetric karyotype.

Difference Between Symmetric and Asymmetric Karyotype in Tabular Form

Summary – Symmetric vs Asymmetric Karyotype

A karyotype can be symmetrical or asymmetrical. An asymmetric karyotype is considered to be a relatively advanced feature compared to symmetric karyotype. Symmetric karyotype has more metacentric chromosomes. Also, all its chromosomes are approximately equal in size. And, they have median or sub-median centromeres. In contrast, asymmetric karyotype has few metacentric chromosomes. Most of the chromosomes are acrocentric in the asymmetric karyotype. Also, the chromosomes differ in size and the positions of the centromeres. Thus, this explains the key difference between symmetric and asymmetric karyotype.

Reference:

1. “Karyotypes | Physical Basis Of Heredity The Nucleus And The Chromosome”. Biocyclopedia.Com, 2020, Available here.
2. “Representing Chromosome Set of Species.” Biology Discussion, 12 July 2016, Available here.

Image Courtesy:

1. “Female Karyotype, 2014” By Hey Paul Studios (CC BY 2.0) via Flickr

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