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Kaguya the Mouse, Middle school

A white lab mouse held in a scientist’s gloved hand

A baby mouse usually comes from one egg and one sperm. Scientists in Tokyo tried to grow a mouse from the DNA of two mouse eggs and no sperm.

Could two eggs and no sperm ever make a living mouse?

2 eggs can make a mouse, with some help

In 2004, scientists in Japan reported a mouse named Kaguya, made from two eggs and no sperm. Some genes carry a tag that says which parent they came from, so two eggs alone cannot make a mouse. One egg came from a newborn mouse whose tags weren’t on yet. That mouse came from a line of mice born missing the piece of DNA that holds the switch for a growth gene.

The head and face of a 13-day-old mouse embryo under a microscope
A printing press presses inked letters onto paper. Print comes from an Old French word that means “to press.”

Your word of the day is

im-PRIN-ting

im-in, into, onfrom Latin in-
printto pressfrom Latin premere
-ingthe action or processfrom Old English -ing

In genetics, a tag on a gene that marks which parent the gene came from. The tag controls whether that copy of the gene switches on.

A scientist in a lab coat looks through a microscope

Eggs and sperm carry the same genes.

If the genes are the same, why does a two-egg embryo stop growing?

A model of the twisted DNA double helix

A clone is an exact copy of one animal’s DNA. Kaguya had no dad. Her DNA came from the eggs of two different female mice, a newborn and an adult.

Is Kaguya a clone of either mouse that gave her DNA?

A scientist holds up a glass jar with a lab mouse inside

Many kids with Prader-Willi syndrome are missing a few genes from dad’s chromosome 15. They still have mom’s copy.

Why can’t mom’s copy of those chromosome 15 genes fill in for dad’s missing copy?

Black-and-white video of a small house mouse sniffing around in the corner of a wall

It took about 460 tries to make one adult mouse, Kaguya.

What do 460 tries for one grown-up mouse tell you about the two-egg method in 2004?

Close-up video of a brown mouse with big ears sitting in a ceramic dish, nibbling sunflower seeds

Kaguya came from an egg of a newborn mouse, and that egg was missing the growth gene switch.

Why would Kaguya’s two egg changes be hard to use in people?

Video of a scientist in a lab placing and studying a specimen slide under a microscope

Eggs and sperm carry the same genes.

Why does a mouse still need DNA from both an egg and a sperm?

Video of a scientist's gloved hand using a pipette to load samples into a gel for a DNA experiment

Lesson complete

Today’s word

imprinting

im-PRIN-ting

In genetics, a tag on a gene that marks which parent the gene came from. The tag controls whether that copy of the gene switches on.

Back to the lessonStart over
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Sources
  1. Tomohiro Kono and colleagues, Tokyo University of Agriculture, Nature, 2004
  2. Philip Leighton, Shirley Tilghman and colleagues, Princeton University, Nature, 1995
  3. Andrew Keniry, Wolf Reik and colleagues, Nature Cell Biology, 2012
  4. Yayoi Obata, Tomohiro Kono and colleagues, Development, 1998
  5. Manabu Kawahara, Tomohiro Kono and colleagues, Nature Biotechnology, 2007
  6. Yanchang Wei, Cai-Rong Yang and Zhen-Ao Zhao, Shanghai Jiao Tong University and UC San Francisco, PNAS, 2022
  7. Review by Denise Barlow and Marisa Bartolomei, Cold Spring Harbor Perspectives in Biology, 2014
  8. MedlinePlus Genetics, US National Library of Medicine, Prader-Willi, Angelman, Beckwith-Wiedemann
  9. Helen Pearson, “Mouse created without father”, Nature News, April 22, 2004
  10. John Travis, “Two egg cells make fatherless mouse”, Science News, May 2004
  11. Vision and Change core concepts and competencies, as summarized in Brownell and others, CBE Life Sciences Education, 2014
  12. Word origins from Dictionary.com: imprinting, imprint, in-, print, -ing, genome, press, pressure, impression, impressionism, espresso
  13. Spanish and French words from Wiktionary: imprimir, imprimer