| Complexity level: | 7 |
| Project cost ($): | 10 |
| Time required: | 1 hour to prepare, 1 day for the science project experiment |
| Material availability: | The participation of pairs of twins of the same race is required |
| Safety concerns: | None |
Hypothesis
Twins have similar physical appearance but different fingerprints.
Overview
Twins
Identical twins are children born from the same pregnancy. They are formed when a fertilized egg splits into two and forms 2 embryos. Both twins will have identical DNA and they will look very much alike. Most twins will also behave very similarly. Fraternal (non-identical) twins are formed when two separate eggs are fertilized at the same time, within the mother’s womb. These twins do not have identical DNA, and may be of opposite sexes.
Who we are and what we become is determined by both nature and nurture. Nature decides the genetic DNA that we inherit from our parents. It determines things like our skin color, hair type, gender, eye color and many more.Nurture also plays a very important role in our development. The environment we grow up in, the people we meet, the experiences we have are among the many factors that help to nurture us. For example, not all identical twins will have the same weight and height as they age. Their actual physical appearances will be determined by the food they eat and the exercise they get, amongst other things.
Interestingly, one difference among identical twins is their fingerprints. The fingerprints of twins may look very similar but they really are not identical.
Scientific Terms
Materials
The materials required for this science fair project:
- A pair of identical male twins (8 to 10 years old)
- A pair of identical female twins (8 to 10 years old)
- A pair of fraternal male-female twins (8 to 10 years old)
- 2 siblings (8 to 10 years old)
- An ink pad
- A piece of paper
- A roll of tissue paper
- 1 measuring tape
- 1 weighing scale
Procedure
1. For this science fair project, the independent variable is the type of twins – identical male twins, identical female twins, male-female fraternal twins and ordinary siblings. The dependent variable is similarity found among the pairs. This is determined by making observations of the twins. The constants (control variables) are the age group, race, country/city of the participants. It is necessary to ensure that all participants are from the same locality and of the same race, to increase the reliability of our results.
2. The twins are examined as pairs, and the following comparisons made.
a. Hair – the similarity of the twins and sibling’s hair.. They are asked if they have used any color dye, straightening or curling of their hair.
b. Facial features – the similarity in the faces of the twins and siblings is observed. The twins are asked if they have had any facial cosmetic surgery.
c. Height – the height of both the twins and siblings is measured against the wall using the measuring tape and compared.
d. Weight – the weight of the twins and siblings is measured using the weighing scale and compared.
e. Eye color – the colors of the twins and sibling’s eyes are compared.
f. Fingerprint – fingerprints of the twins and siblings are taken using the ink pad and placed on a piece of paper. A comparison of the fingerprints is made.
3. The results from procedure 2 are recorded in the table given below.
Results
It was observed that the identical twins had the same type of hair, eye color and facial appearance. Their height and weight were also similar but a slight difference was noted. The twins’ fingerprints looked similar but were not the same. The fraternal twins displayed some similarities, but they were not as identical/similar as the rest of the twin pairs. For the siblings, the hair was similar but everything else was not identical.
| Twin /sibling | Comparing twin appearance and physical attribute | |||||
| Hair | Facial | Height | Weight | Eye color | Fingerprint | |
| Male twins | √ | √ | √ | √ | √ | X |
| Female twins | √ | √ | √ | √ | √ | X |
| Male-female twins | √ | X | √ | X | √ | X |
| Siblings | √ | X | X | X | √ | X |
√ - identical, X – not identical
Conclusion
The hypothesis that identical twins have similar physical appearances but different fingerprints, is proven to be true.
Twins have identical DNA and they cannot be separately identified in a DNA test. Despite having the same DNA and the same appearance, there usually are some slight differences between them that will enable their parents to tell them apart. As the twins age, the different environments they find themselves in will result in differences in their physical appearances.
Also consider
For more reliable results, science experiment should be repeated by increasing the number of participants in each group and tabling the average results.
What do you think your observations would be, if the science project were to be repeated, only this time, by examining the DNA of the different types of twins?
Try to repeat the science project experiment, involving older participants.
References
Why identical twins have different fingerprints? - http://www.forensic-evidence.com/site/ID/ID_Twins.html
Twin - http://en.wikipedia.org/wiki/Twin
Why do identical twins have different heights if they have the same DNA? - http://www.teengrowth.com/index.cfm?action=info_advice&ID_Advice=70822&category=body&catdesc=Body&subdesc=Normal
