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Fingerprint Inheritance Conclusion

Postby isjordan » Sat May 04, 2019 8:43 pm

My daughter did her science project on Fingerprint inheritance. She tested 37 people (20 parents and 17 children). She took all 5 fingerprints on their right hand. Out of the 85 children's fingerprints, 72 matched one of their parents pattern type. My husband says because all 85 didn't match, then she didn't prove that fingerprints are inherited.
What can she do differently with her data? What is the threshold she should've used? This kid worked so hard, but we got off topic when we learned about how loops are more common, and arches are least common. I feel like she had too much information, and nothing concrete to say she proved it.
When asked what she thought couldn't have caused the 13 non matches, she said; 1. unclear fingerprint, 2. she could've miscategorized, 3. DNA comes from farther back than just the parents, they could be a match to a grandparent.
HELP! She is determined to submit it to the regional science fair, and I feel like i need to help somehow.

[Administrator note: project can be viewed here: ... -inherited]

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Re: Fingerprint Inheritance Conclusion

Postby MS15 » Thu May 09, 2019 4:54 pm

Hi isjordan,

This is a very interesting project and I'm sorry to hear about her difficulty in completing it. The hard part is mostly done: the data collection and she did a great job collecting the fingerprints from so many people. All you need now is a way to interpret that data.

First, please check out this project:
It may be helpful for her and you in thinking about the results of the experiment.

Fingerprint patterns are indeed genetically inherited but it's really complex because unlike some other things like eye color which is determined primarily by one gene, fingerprint patterns can be influenced be a large number of genes during development. Read a little bit more here:

Now regarding your some of the points that you brought up:
1. She herself identified 'unclear fingerprints' as a potential cause for some non-matches. I would suggest that she make a note of how many unclear finger prints she has and not use them (and their parents/childrens prints) for the final data analysis. She can always plot a little graph showing what fraction or percentage of the total prints she collected were unclear, and mention that those were not used for the final results. There are always situations like this in any experiment and it is important to be able appreciate what data can actually complicate your conclusion and maybe even throw it off track. It's best to not include that data for making conclusions (but don't lose sight of it either)

2. For all the remaining clear prints where you have full parent/child sets, how about plotting another little graph showing what percentage of the total turned out to be matches? As I mentioned before, fingerprints have complex inheritance and are influenced by many genes so it's hard to set a specific threshold but if you get a number that is higher than 60 or 70%, then it can't purely be by chance.

3. Another thing she can do to make her case more solid, is to take prints from a few unrelated people as well (if there is still time for it). Any random adults who are not parents of the children whose prints she has will do. It doesn't even have to be as big a set as the first time: maybe print 10 individuals. Now she can compare the chances of the kids prints matching their parents versus matching strangers (use only a subset of the parents prints she has, to make number of adult prints the same in both groups). If she finds a much higher chance of your fingerprint matching your parent than a complete stranger, then what is it but genetics?

Hope this is helpful. Please feel free to write back if you need additional assistance. Wish your daughter the best with her project!

P.S. All these graphs in all my three suggestions can be bar charts or pie charts or whatever she likes and looks visually appealing.

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