Difference Between Karyotype and Idiogram

The key difference between karyotype and idiogram is that karyotype is the actual picture of total chromosomes of a cell while idiogram is a schematic diagram of a karyotype that illustrates all chromosome maps.

A set of chromosomes represent the genome and the genetic information of an organism. Each chromosome has a unique shape, size and a set of genes. The number and physical structures of chromosomes reveal important information regarding the organism. Karyotyping is a technique performed to examine the complete set of chromosomes in a cell. Total chromosomes are collected and analyzed during this test to determine whether there are numerical or structural abnormalities in chromosomes. The actual picture that shows the total chromosomes of a cell is the karyotype while the schematic diagram of the total chromosomes of a cell is the idiogram. Both are important in cytogenetic studies.

CONTENTS

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

What is a Karyotype?

A karyotype is a diagram that shows the chromosomal number and constitution in the cells’ nucleus. It consists of a whole set of homologous chromosome pairs, arranged in decreasing series of their size. Microphotographs of metaphase chromosomes help in lining up of the homologous pairs and the preparation of a karyotype. Moreover, it reveals information regarding the number, size, shape, position of centromeres of each chromosome, length of chromosomal arms, presence of secondary constrictions and satellites, etc.

By analyzing the karyotype of the organism, it is possible to detect genetic disorders and other information about the individual. It also tells the gender of the individual. Moreover, it can tell the species to which the individual belongs and the origin and evolutionary relationship among different taxa. Finally, karyotype can determine whether the individual has a chromosomal disorder, which leads to genetic diseases such as Down’s syndrome, Klinefelter’s Syndrome, Turner syndrome and different ploidy conditions, etc.

What is an Idiogram?

Idiogram is a diagrammatic representation or a schematic diagram of a karyotype of a species. Idiogram shows the chromosome maps indicating the locations of genes as bands. It is not an actual picture of total chromosomes of a cell. However, ideogram provides much information about each chromosome. Most importantly, it provides locations of individual genes present in a chromosome.

Moreover, idiograms are useful in identifying various abnormalities associated with a range of chromosomal disorders and determining the links between structural abnormalities and individual genes correlated with various diseases or syndromes.

What are the Similarities Between Karyotype and Idiogram?

• The karyotyping technique gives both karyotype and ideogram.
• Both show the total number of a cell.
• Moreover, they show the morphological features of the chromosomes.
• In both pictures, chromosomes are ordered in a series of decreasing size.

What is the Difference Between Karyotype and Idiogram?

A karyotype is the actual picture of the chromosome set of a cell arranged in homologous pairs and in a series of decreasing size while idiogram is the diagrammatic representation of the karyotype of an individual. So, this is the key difference between karyotype and ideogram. When comparing karyotype and idiogram in terms of identification of regions within chromosomes, it is easy to identify regions within chromosomes in an idiogram than in a karyotype. Therefore, we can consider this as another difference between karyotype and idiogram.

Summary – Karyotype vs Idiogram

Organisms have a specific number and structure of chromosomes. However, due to different reasons, organisms can have unusual numbers of chromosomes and structurally malformed chromosomes. Furthermore, these changes can cause serious genetic disorders. Hence, karyotyping is an important procedure to reveal such genetic conditions in organisms. Karyotyping produces a karyotype showing the actual picture of the chromosome set of an organism. Moreover, idiogram is drawn from the karyotype, and it is a diagrammatic representation of a karyotype. Thus, the karyotype is an actual picture, while ideogram is a diagram. Thus, this is the summary of the difference between karyotype and idiogram.

Reference:

1. “Chromosome Mapping: Idiograms” Nature News, Nature Publishing Group, Available here.
2. “Easy Biology Class.” Easybiologyclass, Available here.

Image Courtesy:

1. “Human male karyotpe high resolution” By Ryan L. Collins doi:10.5281/zenodo.1210135 (CC BY 4.0) via Commons Wikimedia
2. “Human genome idiogram” By National Human Genome Research Institute – Talking Glossary of Genetics (Public Domain) via Commons Wikimedia