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Curiosity Challenge: How Can Lizards Regrow Body Parts?

 
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You may know that some animals, such as reptiles and amphibians, can grow back lost body parts, but how do they do that?
 
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Image via Wikimedia Commons
The process that allows animals, such as reptiles, to grow back their lost body parts is called regeneration. In order to understand regeneration, we must learn about DNA and gene regulation. Every living organism, from bacteria to plants, and including humans, are made up of cells. Cells are known as the smallest unit of living things. Cells are really small, and you need a microscope to take a close look at them. In fact, the human body is made up of trillions of cells! 
 
You may also know that DNA is called the genetic material in our cells. DNA stands for deoxyribonucleic acid, and it contains instructions for our cells. DNA is made up of nucleotides. We have four DNA nucleotides: adenine, thymine, guanine, and cytosine. The specific order of these nucleotides makes up our genetic material, and “packets” of DNA are called genes. You might hear that you get two copies of a gene, one from your mom, and one from your dad. Everybody’s DNA is different because we all have different copies of genes—this make us all unique!
 
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Cells are the smallest units of living things. DNA is the genetic material in cells, and it is contained inside the cell’s nucleus. DNA contains genes with instructions for our cells. DNA is composed of four different nucleotides, and the order of the nucleotides makes us all unique.
When lizards lose their tails, genes are turned on or off that allow them to grow back their tails. Scientists have discovered 326 genes important for tail regeneration. Some of these genes are also turned on during the development of the baby lizard (embryogenesis), and during wound healing. Scientists have found that genes in two complex signaling pathways known as Wnt and MAPK are important for lizard tails to grow back. These two pathways are important for making sure that cells are taking care of themselves. For example, when these pathways are not functioning properly, diseases such as cancer can occur.
 
Scientists believe that when lizards regenerate their tails, cells become “dedifferentiated.” This means that the cells near the injury become more like stem cells, and can be “programmed” to help grow back the tail. This process involves a lot of different genes, and regulation of these genes is what allows the lost body parts to grow back! Some genes are turned on, and some are turned off.
 
Being able to regenerate lost tails can be very helpful for lizards trying to escape predators. Lizards can control when to shed off their tails in a behavior known as autotomy. When a lizard feels it is in danger, it can shed its tail as a self-defense mechanism. The lost tail distracts the predator, and it allows the lizard to flee.
 
One thing to keep in mind is that limb regeneration takes time. The process can take weeks or months for lizards. Regeneration is a very interesting topic, but it is not just for lizards. For example, starfish can also grow back their arms!
 
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Image via Wikimedia Commons
Although you may see lizards grow back their tails all the time on TV, scientists in real life are studying how lizards can regenerate their limbs in order to improve medicine! Hopefully this type of work can help scientists and doctors perform more advanced surgeries and discover better treatments for diseases.
 
Further Reading
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Kenny Chen is a research assistant at MIT earning his PhD in Chemistry. He enjoys biomedical research and is curious about genes and biological processes.
 

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