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Fingerprint Lab

Fingerprint Lab


30-year old murder case solved by Omaha police using this print & FBI's Integrated Automated Fingerprint Identification System (IAFIS)


In this activity, students will examine the epidermal ridge patterns of their fingers using a microscope. They will identify if they have loops, arches or whorls, construct a graph of their class data, and analyze the class data. They will also learn how random events that occur during embryological development can influence their phenotype as adults.




Fingerprints are impressions left by the patterns of friction ridges on a person’s fingertips. Friction ridges are raised portions of epidermis (outer layer of skin cells) found on the fingers, toes, palms and soles. It is thought that these ridges help in gripping and in providing a finer sense of touch. They do this (at least in part) by amplifying vibrations caused when fingers rub against an uneven surface.

Ridge patterns are not a purely heritable trait. Identical twins, (who have identical DNA), do not have identical fingerprints, though they are often very similar. Phenotypes (physical traits) result from the interaction of three factors: Genotype (DNA), Environmental Influences, and Random Developmental Events. Some phenotypes, like human blood type (e.g., A, B, O) are 100% heritable (i.e., there is no influence from the environment or developmental events). Other phenotypes have less heritability. Human height, for example, is thought to have a heritability of 93% (or less, depending on the population and the methodology used), meaning that genetic influences account for 93% (or less) of the variability in human heights in a given population, while environmental influences (particularly access to a diet rich in calcium and protein) also contribute to one’s height. Ridge patterns are believed to result from a combination of these three factors, with random developmental events playing a significant role.

Of the three influences on phenotype, random developmental events are probably the most challenging to explain to students. As a multicellular organism grows and develops, cells divide mitotically to produce clones. However, as cells migrate during development, they may be exposed to slightly different environmental influences, causing their phenotype at maturity to differ from their sister cells, even when they have identical DNA. Many students will already be familiar with the concept of cellular migration, having heard that the surface layer of their epidermis is continually sloughed off and replaced by fresh cells that have migrated toward the surface of the skin from lower layers (see diagram below).

Finger diagram, Grey's Anatomy, from Wiki Commons, public domain

Early in embryological development (4-5 weeks after fertilization), the embryonic skin is made up of a single layer of ectoderm cells above a layer of mesenchyme tissue. As the ectoderm cells divide, they form layers, with new cells migrating from the ectoderm to these various layers. By the eighth week of development, the epidermis is three to four cell layers thick. At around 6.5 weeks, the fetus starts to develop volar pads on its hands. The volar pads, which derive from the mesenchyme tissue and appear like bumps on the palm, influence the ridge patterns that will start to develop at around 10 weeks post-fertilization. After around 24 weeks, the fetus has the same epidermal ridge patterns it will possess for the rest of its life.

Some of the random developmental events that are believed to influence how the ridges form include differential stresses or pressures on various parts of the skin; differential shapes of the volar pads prior to ridge formation; differential timing of ridge formation (e.g., early ridge formation may lead to more whorls).

It is advised to use the term “heritability” with caution, as it is a somewhat controversial and often misunderstood concept. Heritability is a measure of how much of the variability of a trait within a given population is thought to be due to genetic influences (i.e., DNA), in contrast to non-genetic influences like diet, education, socioeconomic status or random developmental events. It is not a probability of an individual’s chances of inheriting a trait. As such, the concept can be instructive in conveying the idea that DNA is not destiny. For example, two tall parents could have a short child either because they were both heterozygous for height or because their child did not get sufficient calcium or protein in its diet.

Determining heritability can be challenging, particularly for behavioral phenotypes or for traits in which no specific genes have been identified. Determining the heritability of intelligence, for example, is problematic not only because there are no known genes or DNA sequences for intelligence that can be measured, but also because it is not entirely clear what intelligence is or how it should be measured. To further complicate matters, the classic heritability studies using twins have a slight bias due to the fact that twins often share a social environment even when separated at birth, drawing into question whether a behavioral similarity was due to a genetic influence or a common environment. Consequently, different investigators, using a variety of different methodologies, have calculated a range of different heritabilities for traits like intelligence, neuroticism and addiction. The heritability table provided on the accompanying Heritability student worksheet likewise gives ranges for several of the traits because the data was derived using different methodologies.


"Fake finger reveals the secrets of touch(external link)," Nature, 29 January 2009, doi:10.1038/news.2009.68

Friction Skin Growth(external link), Furrows and Ridges,

Heritability of adult body height: a comparative study of twin cohorts in eight countries(external link), Silventoinen K, Sammalisto S, Perola M, Boomsma DI, Cornes BK, Davis C, Dunkel L, De Lange M, Harris JR, Hjelmborg JV, Luciano M, Martin NG, Mortensen J, Nisticò L, Pedersen NL, Skytthe A, Spector TD, Stazi MA, Willemsen G, Kaprio J., Department of Public Health, University of Helsinki, Finland. Twin Res. 2003 Oct;6(5):399-408.

Heritability(external link), Wikipedia,

LEARNING GOALS(Students Will Be Able to):

Describe the role of various cell and tissue types that contribute to the formation of epidermal ridges on the fingers Use the development of epidermal ridges as a model for cellular division and differentiation Use statistics and probability to explain the variation of fingerprint types within a population Create a graph of class data on fingerprint variability


Students should be familiar with the concepts of genotype and phenotype, mitosis, basic microscopy and the scientific process. A good lead-in activity is the accompanying heritability quiz and worksheet.


The heritability survey and worksheet can be assigned on day 1 and the lab activity on day 2.


The survey should take only a few minutes to complete. The class discussion that follows should be limited at the teacher’s discretion. The quiz, discussion and heritability worksheet can be completed in 20-50 minutes, depending on how much class time is devoted to debriefing them. The worksheet can also be completed as a homework assignment and debriefed prior to the lab.

On Day 2, students should be able to lift their own fingerprints in 5-10 minutes. Because it will take time for all students to complete this, some students will likely finish early and have to wait for their classmates in order to collect the class data. The total length of the lab will vary depending on the number of microscopes available and whether or not you want students to take digital photographs. Students should be able to complete the entire lab, including the graph and analysis questions within a 50 minute class period.


Each student team should have one low power microscope with top illumination, 1 roll of scotch tape, 1 copy of the “How to Identify Fingerprints” handout (laminated or inserted into plastic sheet protectors)


Make copies of the heritability survey (1 per student) Make copies of the heritability worksheet (1 per student) Make copies of the lab handout (1 per student) Make copies of the “How to Identify Fingerprints” handout (1 per student team, laminated or inserted into plastic sheet protectors) Set up student lab stations with microscopes (and computers, if using digital scopes)


Pass out the heritability surveys and explain that heritability is how much the genes or DNA influences the trait. Give students a few minutes to complete the surveys and then solicit responses. Rather than telling students if they are right or wrong, challenge them to support their ideas with examples or evidence.


Day 1

1. Do the anticipatory set one day prior to the actual lab activity

2. Pass out the heritability worksheets and have students complete them. If you are short on time, these can be completed as a homework assignment. However, it is also an excellent activity for students to do collaboratively in small groups.

3. Have a class debriefing of the heritability worksheet, with students sharing their responses and explanations. You could also use this time to discuss some of the other traits listed in table 1.

Day 2

4. Read through the procedure with students. Review how to use the microscopes. If you have an LCD projector, it can be helpful to project images of the various types of fingerprints (see accompanying handout, “How to Identify Fingerprints.”) You also want to model for students how to transfer the fingerprint to the lab handout using scotch tape.

Fingerprint "dusting." (Image by Michael Dunn, Creative Commons)

5. Have students go to their lab stations and complete their individual prints. Assist as needed. The microscopes can be used to help identify the ridge patterns and, if digital scopes are available, to take digital images of the prints. They must have top illumination and should be low power (10-20x)

Pinky fingerprint taped to page, 10x, Celestron, Image by Michael Dunn, Creative Commons

6. When everyone has finished and cleaned up, have students provide their individual data to be added to the class totals. The teacher or a student can record these on the board for everyone to copy.

7. Students can then prepare bar graphs of the data using graph paper, Excel or other software.

Alternative Version Day 2

If you have digital microscopes, students can skip the pencil and tape part of the procedure and take direct digital images of their fingerprints and either print these out to tape to their lab reports or digitally cut and paste the images into a computer printed lab report.


(Image from the U.S. Dept of Commerce, Public Domain)

Class totals will vary from class to class. However, typically loops are most common (65-75%), followed by whorls (20-30%), and arches (5-10%). There are variations on each of these patterns, as shown in the image below. Loops can point toward the left or the right and sometimes look like arches. The main point of distinction is that with arches, the ridge lines enter from one side and leave on the other, whereas with loops, the ridge lines enter and exit on the same side. There are almost always two deltas with whorls, one with loops and none with arches.

(Image from the FBI website).


Next Generation Science Standards

MS-LS3-2. Develop and use a model to describe why asexual reproduction results in offspring with identical genetic information and sexual reproduction results in offspring with genetic variation.

HS-LS1-2. Develop and use a model to illustrate the hierarchical organization of interacting systems that provide specific functions within multicellular organisms.

HS-LS1-4. Use a model to illustrate the role of cellular division (mitosis) and differentiation in producing and maintaining complex organisms.

HS-LS3-3. Apply concepts of statistics and probability to explain the variation and distribution of expressed traits in a population.

Common Core State Standards

CCSS.Math.Content.7.SP.A.1 Understand that statistics can be used to gain information about a population by examining a sample of the population; generalizations about a population from a sample are valid only if the sample is representative of that population. Understand that random sampling tends to produce representative samples and support valid inferences.

CCSS.Math.Content.7.SP.A.2 Use data from a random sample to draw inferences about a population with an unknown characteristic of interest. Generate multiple samples (or simulated samples) of the same size to gauge the variation in estimates or predictions. For example, estimate the mean word length in a book by randomly sampling words from the book; predict the winner of a school election based on randomly sampled survey data. Gauge how far off the estimate or prediction might be.

CCSS.Math.Content.HSS-ID.A.1 Represent data with plots on the real number line (dot plots, histograms, and box plots). CCSS.ELA-Literacy.RST.9-10.3 Follow precisely a complex multistep procedure when carrying out experiments, taking measurements, or performing technical tasks, attending to special cases or exceptions defined in the text.

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