Questions for ‘Living mysteries: This critter has 38 times more DNA than you do’

A underwater photo of a Neuse River waterdog, a salamander with mottled brown and tan skin and red gill tufts just behind its head. It is resting on a bed of river rocks.

The Neuse River waterdog (Necturus lewisi) has the largest genome of any four-footed animal on Earth, 38 times the size of the human genome. This salamander inhabits two small river drainages in North Carolina. It is currently listed as a threatened species.

Melissa McGaw/NC Water Resources Commission

To accompany ‘Living mysteries: This critter has 38 times more DNA than you do


Before Reading:

  1. Research the term DNA. (Try starting here or here.) What is DNA? How does it influence an organism’s features?
  2. How might an organism might be affected by the amount of DNA in its cells?   

During Reading:

  1. What is so strange about the Neuse River waterdog’s life cycle?
  2. What is a genome? How do the sizes of salamander genomes compare to those of other animals? How does genome size affect the life cycles of salamanders? (Use information from the story to support your answer.)
  3. Why do salamanders have so much more DNA than other animals? How does the number of genes in salamanders compare to that in other animals?
  4. What are transposons? What effects can transposons have on their host? Why do some scientists think of them as parasites? How can hosts defend themselves against transposons?
  5. What does it mean to “sequence” DNA? What did Rachel Mueller discover when she sequenced the DNA of salamanders?
  6. What does it mean for genes to “turn on”? Why does it take so long for genes to turn on in salamanders? How can this affect their development?
  7. How big are salamanders’ cells compared to those in people? What affects cell size in salamanders? How does this affect salamanders’ bodies? 
  8. How might huge genomes affect the ability of salamanders to grow back lost body parts?
  9. How might salamanders’ slow life cycle help them survive having a huge genome? Use information from the story to support your answer.
  10. What survival needs likely prevent the genomes of other types of animals, such as birds, from getting so big?

After Reading:

  1. Think about the potential advantages — and disadvantages — of having a huge genome (as explored in this article). From that information, design a new kind of animal. What size genome would you give it? A genome as small as a bird’s? Something midsize, like a human’s? Or something giant, like a salamander’s? Explain your answer. What features would an animal with that size of genome have? For what types of ecosystems or lifestyles would your animal be well suited?