“Who Dunnit”

Modeling the Use of DNA Evidence in Crime Solving


Pauline Hudson

Isaac E. Young Middle School, New Rochelle, N.Y.


Summer Research Program for Science Teachers

August 2012




Subject: The Living Environment (Biology)/General science


Grade levels: 8th and 9th


Time: 2 period  (80 minutes)


Purpose: Students test blood types and perform DNA analysis to find evidence in a crime study.


Students will be able to:

1. Determine the blood type of samples of imitation blood.

2. Analyze the results of a model DNA genotyping procedure

3. Make conclusions, based on evidence in a crime study.


Materials per group of 4 students:

1 Blood typing kit.* (Kit Prep Worksheet)

1 Set of color coded DNA strands.

1 Pair of scissors labeled restriction enzymes.

4 Procedures and results worksheets (Blood Type Procedure and Crime Analysis Report)


*Blood typing material is made using simulated blood.


Background: Students will need to have prior knowledge of ABO blood types, and DNA structure. Use smart board or poster session to review those concepts in pre lab session or 20 mins of the double period for this lesson.


Essential Questions:

1. How is blood used as evidence in crime solving?

2. What are some tests that are helpful to determine who blood belongs to?

3. Explain why blood type results are not sufficient evidence to convict a person of a crime.

4. How is DNA useful in confirming the source of the blood?


Procedure: Students will follow procedure on Worksheet 1 and answer questions on Worksheet 2.

New York State Living Environment Standards


Standard 1- Students will use scientific inquiry to pose questions, seek answers and develop solutions.


1.2a Inquiry involves asking questions and locating, interpreting and processing information from a variety of sources


Standard 4- Students will understand and apply scientific concepts, principles and theories pertaining to the Physical Setting and Living Environment and recognize the historical development of ideas in science.


2.1c. Hereditary information is contained in genes, and located in the chromosomes of each cell. An inherited trait of an individual can be determined by one or by many genes, and a single gene can influence more than one trait. A human cell contains many thousands of different genes in its nucleus.


2.1e. In sexually reproducing organisms, the new individual receives half of the genetic information from its mother (via the egg) and half from its father (via the sperm).Sexually produced offspring often resemble, but are not identical to, either of their parents.


2.1f. In all organisms, the coded instructions for specifying the characteristics of the organism are carried in DNA, a large molecule formed from subunits arranged in a sequence with bases of four kinds (represented by A, G, C, and T). The chemical and structural properties of DNA are the basis for how the genetic information that underlies heredity is both encoded in genes (as a string of molecular bases) and replicated by means of a template.