Science Project:

The Genetics of Eye Color

3.5 based on 16 ratings

The purpose of this project is to discover eye-color genotypes that could be present in a given population. This study will take into account dominant and recessive traits as well as the evolving understanding of the genetics of eye color.

  • How are genes passed down from parents to their offspring?
  • How many eye-color alleles does each person have?
  • How many eye-color alleles can one person pass to their offspring?
  • Are dominant or recessive genes passed down more frequently?
  • How can two brown-eyed parents have a blue-eyed baby?
  • Why is it difficult fortwo blue-eyed parents to have a brown-eyed baby?
  • What is the difference between genotype and phenotype?
  • How can you determine possible genotypes?
  • Are blue eyes or brown eyes more common?

Mendel first identified simple dominant and recessive traits in his famous experiments on pea plants. In human beings, a baby receives one set of genes from its father and another set from its mother. The combination of all of these genes, and the often complicated interactions between them, give the baby many of its physical characteristics, including its eye color. It was formerly thought that just two genes influenced eye color. However, it was recently discovered that the first gene is actually two distinct genes! Although eye color ismuch more complicated than we initially thought, for the purposes of this projectwe'llkeep things simple and focus on more common cases and the interaction ofdominant and recessive traits.

The following example shows the possible genetic outcomes for a father with Bb and a mother with Bb.

Father’s Genotype

Bb (one gene for dominant BROWN and the other for recessive blue)

Father’s Phenotype

Because only one gene must be dominant to show the dominant trait, the father has brown eyes.

Mother’s Genotype

Bb (one gene for dominant BROWN and the other for recessive blue)

Mother’s Phenotype

Because only on gene must be dominant to show the dominant trait, the mother has brown eyes.

As each parent will only pass down one of their two alleles to their offspring, we can determine what combinations are possible using a chart such as this:
Father →

BROWN (B)

blue (b)
Mother ↓

BROWN (B)

BB (brown eyes)

Bb (brown eyes)

blue (b)

bB (brown eyes)

bb (blue eyes)

  • A number of willing participants who have living grandparents.
  • Graph paper

:

  1. Find a number of people willing to help you by providing data about their eye color for your study. It is helpful to have information for at least three generations, so try to find volunteers with living grandparents.
  2. Record the eye-color of your volunteer on a chart. You will call this person Subject A and place them in the “Generation 0” line of the chart.
  3. If the subject has brothers or sisters, collect data on them as well. Do not include the data if the siblings do not share both parents with the subject.
  4. Collect data on the eye-color of Subject A’s parents. Place this information on Generation -1 of the chart.
  5. If data is available for siblings of Subject A’s parents, collect this information as well. Again, do not include data if siblings do not share both parents.
  6. Collect data on the eye-color of Subject A’s grandparents. Place this information on the Generation -2 line of the chart.
  7. If data is available for siblings of Subject A’s grandparents, collect this information as well. Again, do not include data if siblings do not share both parents.
  8. If data can be collected for any previous generations, collect this information as well, following the same parameters.
  9. Deduce the possible genotypes for the people whose genetics are not obvious.
  10. Check your answers by determining if the genotype you think they have can produce the eye colors found in their offspring.
  11. You can take this further by determining the mathematical probability that your subject has one or another genotype.
  12. It is also possible to repeat this experiment with multiple subjects. This will give you an idea of the likelihood of specific genotypes in a larger population.

Terms/Concepts: Mendel; Dominant gene; Recessive gene; Genetics; Inherited traits; Eye colors; Genotype; Phenotype; Allele

References:

Author: Crystal Beran
Disclaimer and Safety Precautions

Education.com provides the Science Fair Project Ideas for informational purposes only. Education.com does not make any guarantee or representation regarding the Science Fair Project Ideas and is not responsible or liable for any loss or damage, directly or indirectly, caused by your use of such information. By accessing the Science Fair Project Ideas, you waive and renounce any claims against Education.com that arise thereof. In addition, your access to Education.com's website and Science Fair Project Ideas is covered by Education.com's Privacy Policy and site Terms of Use, which include limitations on Education.com's liability.

Warning is hereby given that not all Project Ideas are appropriate for all individuals or in all circumstances. Implementation of any Science Project Idea should be undertaken only in appropriate settings and with appropriate parental or other supervision. Reading and following the safety precautions of all materials used in a project is the sole responsibility of each individual. For further information, consult your state's handbook of Science Safety.

How likely are you to recommend Education.com to your friends and colleagues?

Not at all likely
Extremely likely