Shop Windows to the Universe

Science, Evolution, and Creationism, by the National Academies, focuses on teaching evolution in today's classrooms. Check out the other publications in our online store.

Patterns of Inheritance

Aunt Maggie says you have your father's eyes.
Grandma says you have your mother's smile.

Could you actually have the traits from these other people? If you are genetically related to them then yes, you could. Half of your genes are from your mother and half are from your father. But you might look more like one of them than the other. Why is that? Genes are shuffled during meiosis, bringing together different mixes of genes in each gamete. Thus, your brother might look more like one of your parents while you look more like the other.

Within each of the trillions of cells in your body are chromosomes. Chromosomes come in pairs. You got one chromosome of each pair from your mother and one from your father. Along each chromosome are genes, one for each trait. This means that you have two copies of each gene, one from your mother and one from your father. Both genes of a pair deal with the same trait, but they might differ in their information about it. For instance, one gene for eye color might say blue while the other one says brown.

  • If the two genes are actually the same, for instance, if both genes give instructions for blue eyes, then the genes are called homozygous.
  • If the two are different, for instance, if one is for blue eyes and the other is for brown eyes, then the genes are called heterozygous.

In a heterozygous situation, the two genes have different instructions. Often one of those genes wins out and its instructions are carried out (that's called the dominant gene). The other one is still present but its instructions are not carried out (that's called a recessive gene). As a custom, people designate dominant genes with uppercase letters and lowercase genes with lowercase letters. For example gene "A" is dominant and gene "a" is recessive.

The genes of an individual are called its geneotype. They determine what it will look like, which is called its phenotype!

Last modified February 29, 2008 by Lisa Gardiner.

Shop Windows to the Universe Science Store!

"Science, Evolution, and Creationism", by the National Academies, provides fascinating background on these topics for all, and is particularly useful for the Earth and space science classroom. Check our other books in our online store.

Windows to the Universe Community

News

Opportunities

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

Chromosomes, DNA and Genes: Tiny Things That Have a Huge Effect on Who We Are!

Do you look a bit like your siblings? Do you and your siblings look a bit like your parents? The similarities are because, unless you were adopted, you and the other members of your family have genetic...more

Cell Division by Meiosis

Plants, animals and many other species within the domain Eukaryota are able to make more individuals by sexual reproduction. In its simplest form, this means that offspring are made from gametes. Gametes...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

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

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