This Punnet square shows to possible combinations of genes in the children of parents that both have the genotype "Ee".
Click on image for full size
Windows to the Universe original image

Answers to the Genetic Puzzle!

  1. Mary must have two recessive genes to have attached earlobes, so her genotype is “ee”.
  2. If Mary inherited a recessive gene from each parents, then both of her parents must have the recessive gene “e” in their genotypes. However, if both of them have free hanging lobes, then they must also have the dominant gene “E”. So, both parents must have the genotype “Ee”
  3. If Fred also has free hanging lobes, the dominant trait, then at least one of his genes must be dominant (“E”). Did you figure out the possibilities for the other gene based on the parents’ genotypes? The picture at the left shows what the Punnet Square looks like.

With two parents that have the genotype Ee, there are three possible outcomes for the genotypes of the children.

  • One out of four (or 25%) will likely have the genotype “ee” (attached earlobes)
  • Two out of four (or 50%) will likely have the genotype “Ee” (free hanging lobes)
  • One out of four (25% will likely have the genotype “EE” (also free hanging lobes)

So, Fred could have a genotype of “Ee” or “EE”!

Last modified April 13, 2004 by Lisa Gardiner.

You might also be interested in:

Traveling Nitrogen Classroom Activity Kit

Check out our online store - minerals, fossils, books, activities, jewelry, and household items!...more

Can there be Life in the Environment of Jupiter?

Jupiter's atmospheric environment is one of strong gravity, high pressure, strong winds, from 225 miles per hour to 1000 miles per hour, and cold temperatures of -270 degrees to +32 degrees (freezing temperature)....more

The possible discovery of Life on Mars

In July, 1996, it was announced that Dr. David McKay, along with a team of scientists at Johnson Space Center (a division of NASA), had discovered possible fossils of bacteria in an ancient rock from Mars....more

The Environment of Saturn

Saturn's atmospheric environment is one of strong gravity, high pressure, strong winds, from 225 miles per hour to 1000 miles per hour, and cold temperatures of -270 degrees to +80 degrees. With winds...more

The Environment of Titan, can there be Life?

Titan's atmosphere is a lot like the Earth's, except that it is very cold, from -330 degrees to -290 degrees! Like the Earth, there is a lot of Nitrogen and other complex molecules. There also may be an...more


Autotrophs are organisms that produce organic compounds from an inorganic source of carbon (carbon dioxide) given a source of energy. If the source of energy is the reactions of inorganic chemical compounds,...more


In the warm primordial ocean, aggregates of amino acids, proteins, and other hydrocarbons coalesced into a form called *coacervates*. Organic polymers such as amino acids will spontaneously form coacervates...more

Early Life

Organisms that are able to make their own food (in the form of sugars) by using the energy of the Sun are called autotrophs, meaning "self-feeders". Photosynthesis is the name of the process through which...more

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA