Middle School Science Lessons

This is a fun and creative activity to tie all of the following concepts together into one lesson: DNA sequencing & transcription, mRNA translation, amino acid codons & proteins, genotype, phenotype, recessive & dominant alleles & traits. (updated 4/27/25)

Objectives: Students will help solve a crime based on DNA evidence left at the crime scene. There are 3 scenarios that will identify 3 different criminals – this avoids having the kids tell the next class who the suspect is. Each student will receive one of the 4 DNA samples – you can have students work individually, or have a group of students work together on suspect 1, another on suspect 2, etc. (Sorry – I do not have an answer key to post)

Lesson Resources:

• Student Handouts – includes 3 scenarios with different suspects.
  • To edit it and add your teachers or make your own version of the story, make a copy of the Google Doc
  • Print out and cut apart the DNA samples
  • Students will randomly receive one of the 4 suspect’s DNA samples
• Amino Acid Codon Wheel– reference for decoding, I prefer the wheel shape instead of the data table
• DNA Cheat Sheet – reference that summarizes DNA and protein synthesis, Google Doc, make a copy to edit
• Compound Interest Amino Acid Molecules (pdf) – reference sheet of the amino acids molecules

Model how to do the first box of the crime data worksheet (some students won’t have this exact sequence on their DNA sample) and how to use their reference charts to decode the DNA:

DNA	ACC	GGT	TCT
RNA	UGG	CCA	AGA
Amino Acids	TRP – PRO – ARG
Phenotype/Trait	Hairy
Genotype	hh

• Directions:
  • Step 1 – students will transcribe the DNA sequences into mRNA sequences
  • Step 2 – using the Amino Acid codon wheel, they will determine the amino acid for each codon
  • Step 3 – using the chart, they will find protein using the sequence of amino acids
  • Step 4 – using the proteins, they will determine the phenotype
  • Step 5 – using the phenotypes, they will determine the genotype(s)
  • Step 6 – is their suspect the criminal?
  • Step 7 – they will draw a mug shot of their suspect using the phenotypes they decoded
  • Step 8 – hang up the mug shots and create a gallery of suspects

This lesson was modified from the one found on Biology Corner: https://www.biologycorner.com/worksheets/DNA_snorks.html