Difference Between Chimeric and Transgenic Organisms

The key difference between chimeric and transgenic organisms is that chimeric organisms are single organisms composed of cells with more than one distinct genotype, while transgenic organisms are organisms created by inserting foreign DNA into the genome.

Genetic engineering, also called genetic modification or genetic manipulation, is the direct manipulation of organisms’ gene or genotype using biotechnological techniques. Chimeric and transgenic organisms are genetic modifications. A chimeric organism is a result of combining the cells of two or more genetically distinct individuals. When the genetic material (DNA) of one organism combines or inserts into another, it results in a transgenic organism.

CONTENTS

1. Overview and Key Difference
2. What are Chimeric Organisms
3. What are Transgenic Organisms
4. Similarities Between Chimeric and Transgenic Organisms
5. Side by Side Comparison – Chimeric vs Transgenic Organisms in Tabular Form
6. Summary

What are Chimeric Organisms?

Chimeric organism is an organism whose body is composed of cells that are genetically distinct (distinct genotype). In laboratories, scientists create chimaeras whose bodies are a mix of cells from different species. For example, chimeric pigs are pigs with a few monkey cells in most of their organs.

An animal that develops from a single fertilised egg should have exactly the same genome. But, chimaeras arise in several different ways. The most dramatic way is when two embryos that would normally develop into non-identical twins fuse in the womb. The resultant individual parts are derived from one embryo and parts from the other embryo. People with this kind of chimerism appear fully normal. For this reason, chimerism is accidentally found. But sometimes there are signs, such as different coloured eyes or patches of skin of different shades, etc. When an individual is a mix of male and female cells, there can also be some abnormalities in the reproductive system.

Most commonly in pregnancy, the cells of mothers and babies can be exchanged. Therefore, the mothers have cells from their babies which are growing in various parts of their body after pregnancy. These cells can survive for at least 40 years in the mother’s bodies. This type of chimerism is called microchimerism. Furthermore, chimerism can also occur from the organ transplantation process.

What are Transgenic Organisms?

Transgenic organism is an organism that contains foreign DNA that has been introduced using biotechnological techniques. The foreign DNA is called the transgene. Transgene is defined as the DNA from another species or laboratory manipulated DNA from the same species. Transgenic organisms are also termed genetically modified organisms (GMO). The process of creating transgenic organisms is called transformation or transfection.

In the transgenic process, the DNA must first be transferred across the cell membrane without destroying the cell. The naked DNA can be transferred into the cell by adding DNA to the medium and temporarily increasing the porosity of the membrane (electroporation). Other methods such as vectors to transport DNA across the cell membrane are also used.

The rate of transcription of a transgene is highly dependent on the state of the chromatin into which it is inserted, which is known as the position effect. Other factors also influence the success of the entire transgenic process. Through the transgenic process, it is possible to make transgenic plants, animals, and microorganisms.

What are the Similarities Between Chimeric and Transgenic Organisms?

• Both are genetic modifications.
• Both processes have unintended medical consequences.
• They bring out evolutionary changes in the organism.
• These processes can be implemented in plants and animals.

What is the Difference Between Chimeric and Transgenic Organisms?

A chimeric organism is a single organism composed of cells with more than one distinct genotype. In contrast, a transgenic organism is an organism created by inserting foreign DNA into the genome. Thus, this is the key difference between chimeric and transgenic organisms. Moreover, the process of creating a chimeric organism does not always bring changes to phenotype, while the process of creating the transgenic organism always brings changes in phenotype.

The below infographic lists the differences between chimeric and transgenic organisms in tabular form.

Summary – Chimeric vs Transgenic Organisms

Genetic engineering is the process of altering the genetic makeup of an organism. Genetic engineering often generated fear in the general public. Therefore, lots of ethical concerns are involved in the modern genetic engineering process. A chimera is a single organism composed of genetically distinct cells. In contrast, a transgenic organism has an altered genome due to a foreign gene. Thus, this is the summary of the difference between chimeric and transgenic organisms.

Reference:

1. Page, Michael Le. “What Is a Chimera?” New Scientist, Available here.
2. “Transgenic Organisms.” Genetics Generation, 19 Feb. 2019, Available here.

Image Courtesy:

1. “Backcrossing mice from chimera edit” By Upirix – Own work (CC BY-SA 4.0) via Commons Wikimedia