C.S.I.

DNA Discovery: Extracting Genetic Material from Strawberries

By: Meghan Thoreau, OSU Extension Educator, Community Development & STEM, Pickaway County

This month, we’re diving into the fascinating world of DNA and genetics! We’re exploring the structure and function of DNA, how genetic traits are passed down, and the incredible ways DNA science is used in our daily lives. From solving crimes to developing new medicines, understanding DNA has revolutionized many fields. We’re learning how DNA is extracted, analyzed, and applied in various areas, including medicine, agriculture, and forensics.

In our DNA Strawberry Extraction lab, we’ll get hands-on experience extracting DNA from strawberries using simple household items. This fun and interactive activity will help us understand the basics of DNA extraction and its significance in the scientific world.

DNA Strawberry Extraction Supplies

DNA, or deoxyribonucleic acid, is the molecule that contains the genetic instructions for all living organisms. It’s often referred to as the “blueprint of life.” DNA is found in the cells of every living thing, from humans to strawberries. But have you ever wondered what DNA looks like or how it’s extracted from cells? In this activity, we’ll explore the fascinating world of DNA by extracting it from strawberries using simple household items. Get ready to uncover the genetic secrets of one of nature’s sweetest treats!

Steps in Strawberry DNA

Strawberries are unique because they are octoploid, meaning they have eight copies of each chromosome. This abundance of DNA makes strawberries a great model for DNA extraction labs, as it’s easier to visualize the DNA strands. For comparison, human cells are diploid, with only two copies of each chromosome.

This activity combines hands-on experimentation with critical thinking and problem-solving, providing a comprehensive learning experience for students.

The science behind the DNA Strawberry Extraction Lab:

Breaking Down Cell Walls and Membranes:

  • Blending strawberries: The blender breaks down the cell walls of the strawberry tissue, releasing the cellular contents. This mechanical disruption helps to release the DNA from the cells.
  • Dish soap (detergent): The soap breaks down the cell membranes (lipid bilayer) and nuclear membranes, releasing the DNA and other cellular contents. The detergent helps to solubilize the lipids and disrupt the membrane structure.

Releasing DNA from Proteins:

  • Salt: The salt helps to release the DNA from proteins that are bound to it. The positively charged sodium ions (Na+) from the salt help to neutralize the negative charge on the DNA phosphate backbone, allowing the DNA to precipitate out of solution more easily.

Precipitating DNA:

  • Rubbing alcohol (ethanol): When the ethanol is added to the mixture, it creates a layer on top of the strawberry mixture. DNA is insoluble in ethanol, so it precipitates out of solution and forms a visible, stringy substance at the interface between the alcohol and the strawberry mixture. This is because the ethanol disrupts the hydrogen bonds between the DNA and water, causing the DNA to come out of solution.

Why Strawberries?

  • Octoploidy: Strawberries are octoploid, meaning they have eight sets of chromosomes (one set from each parent, duplicated). This means they have a large amount of DNA, making it easier to extract and visualize.
  • Easy to break down: Strawberries are soft and easy to blend, making it simple to break down the cell walls and release the DNA.

DNA Structure and Properties:

  • Double-stranded helix: DNA is a double-stranded molecule with sugar and phosphate molecules making up the backbone, and nitrogenous bases projecting inward from the backbone and pairing with each other in a complementary manner.
  • Chargaff’s rules: The base pairing rules (A-T and G-C) help to explain the structure and properties of DNA.
  • Negative charge: DNA has a negative charge due to the phosphate groups in the backbone, which is important for its interactions with other molecules.

This lab takes advantage of the properties of DNA and the cellular structure of strawberries to make DNA extraction and visualization possible. By understanding the science behind the lab, students can gain a deeper appreciation for the molecular biology of DNA.

Learning about DNA extraction has numerous real-world applications across various fields

Forensic Science:

  • Crime scene investigation: DNA extraction is crucial in forensic science for analyzing DNA evidence, identifying suspects, and solving crimes.
  • DNA profiling: DNA extraction is used to create DNA profiles, which can be used to identify individuals, resolve paternity disputes, and identify human remains.

forensic scientist at work

Genetic Engineering and Biotechnology:

  • Genetically modified organisms (GMOs): DNA extraction is used to introduce desirable traits into organisms, such as pest resistance or improved nutritional content.
  • Gene therapy: DNA extraction is used to develop gene therapies that can treat genetic disorders by modifying or replacing faulty genes.

Medical Research and Diagnostics:

  • Genetic testing: DNA extraction is used to diagnose genetic disorders, identify genetic mutations, and predict disease susceptibility.
  • Cancer research: DNA extraction is used to study cancer genetics, identify biomarkers, and develop targeted therapies.

dna for cancer testing

Agriculture and Food Science:

  • Crop improvement: DNA extraction is used to develop crops with desirable traits, such as drought resistance or improved yield.
  • Food safety testing: DNA extraction is used to detect and identify pathogens in food, ensuring food safety and quality.

Conservation Biology:

  • Species identification: DNA extraction is used to identify species, study population genetics, and monitor biodiversity.
  • Endangered species conservation: DNA extraction is used to study the genetics of endangered species and develop conservation strategies.

Personalized Medicine:

  • Genomic medicine: DNA extraction is used to develop personalized treatment plans based on an individual’s genetic profile.
  • Pharmacogenomics: DNA extraction is used to predict an individual’s response to certain medications based on their genetic profile.

DNA Fingerprinting:

  • Food authentication: DNA extraction is used to verify the authenticity of food products and detect adulteration.
  • Product tracing: DNA extraction is used to track the origin and movement of products, ensuring supply chain integrity.

DNA tagging process

These are just a few examples of the many real-world applications of DNA extraction. The knowledge and skills gained from learning about DNA extraction can be applied to various fields and industries, leading to innovative solutions and discoveries.

 

Color Science, Abstract Art, and a C.S.I. Chromatography Lab Challenge

By: Meghan Thoreau, OSU Extension Educator

Enjoy the program highlight video above. This past November students engaged in several hands-on activities that allowed them to learn more about chemistry by adding a little color to it.

Chemistry of Milk and Soap Molecules 

First students experimented in a rainbow milk activity where they learned first hand about how cow’s milk and soap molecules interact with each other by add food coloring to the mix to visual the reaction.

milk chemistry poster

https://i0.wp.com/www.compoundchem.com/wp-content/uploads/2018/06/The-chemistry-of-milk-v2.png?ssl=1

Cow’s milk contains water, fat globules, proteins, minerals, and vitamins that are spread throughout the liquid. Of this composition, fats and proteins are very sensitive to changes in the milk solution they comprise. Whereas detergent, such as dish soap is made up of anionic, non-ionic, and amphoteric surfactants.

soap chemistry poster

https://i0.wp.com/www.compoundchem.com/wp-content/uploads/2018/05/The-chemistry-of-a-dishwasher.png?ssl=1

Sufactants help with wetting, degreasing, and foaming in the washing processes, where as non-ionic surfactants improve the functional properties of liquids, so they act as surfactant auxiliaries.

https://melscience.com/BE-en/chemistry/experiments/colors-v2_milk/

What happens chemically with the soap molecules and the fats in the milk?

The soap’s polar, or hydrophilic (water-loving), end dissolves in water, and its hydrophobic (water-fearing) end attaches to a fat globule in the milk. The molecules of fat bend, roll, twist, and contort in all directions as the soap molecules race around to join up with the fat molecules.

 

experimenting with milk and soap

Student adding soap molecules to milk sample.

What does the term hydrophilic mean?

Well let’s break it down. The  prefix “hydro” means water and the suffix “philic” means loving. Thus hydrophilic means water-loving. A hydrophilic molecule is a molecule that can mix and interact with water.

water loving diagram

To observed this chemical interaction, we added food coloring drops into the milk, dipped a tooth pick or q-tip into dish soap and poked it into the milk and chemistry was witnessed before their very eyes.

The opposite of hydrophilic is hydrophobic, substances that repel water, “hydros” for water and “phobos” for fear.

More Hydrophobic and Hydrophilic Interactions: Creating Abstract Art by Applying Chemistry

 

abstract art

Student created abstract art by applied chemistry.

To continue reinforcing this concept of molecular play, students were lead through another chemistry experiment were they made abstract art with shaving cream, food coloring, and paper.

Soap is an interesting molecule because it has both hydrophilic and hydrophobic components, or what we call amphipathic, depicted in the image above. A soap molecule looks a bit like a snake, in which the head is polar and hydrophilic and the tail is non-polar and hydrophobic.

soap molecule diagram

https://www.themacbath.com/blog/2016/6/27/back-to-basics-what-is-soap

Shaving is a foam that is comprised of soap and air. Food color is a dye that was dissolved in water, and is therefore hydrophilic. Students added a few drops of food coloring into a tray of shaving cream. The food coloring can only interact with the hydrophilic head of the soap molecules and thus has limited mobility.

The students take advantage of this limited mobility characteristic of the shaving cream’s chemistry and take a tooth pick and swirl the drops of food coloring for a few seconds. They then take a sheet of paper and place it on top of their shaving cream and add a little pressure.

Paper is composed of cellulose with is comprised of polar hydroxyl (or oxygen and hydrogen) that make paper very hydrophilic. The food coloring which is also very hydrophilic, can spread very easily across the paper to stamp a distinct pattern from the shaving cream to the paper; similar to a printing press, but her used for abstract art printing.

Chromatography C.S.I. Lab

The students started the last experiment, by learning how science terms can be broken down and be very informative by just understanding how terminology is used. For example, the club activity used Chromatography,  chromat/o means “color” and –graphy means “the process of recording,” therefore chromatography is “the process of recording color.” The break down of science terms can be very specific and informative to learning.Just like photography is “the process of recording a light” which was the original science process behind how traditional photographs were developed.

Or take Instagram, the social media company, used a terminology naming approach to describe their social media site. Insta- means “instant” or quickly produced. Gram means “to record,” so Instagram means “to record instantly.”

Students preparing to start the C.S.I. Chromatography lab experiment.

Now back to the student run C.S.I. Lab experiment, students began lab technicians that analyzed evidence in theft case of, Who done it? The were given six different pens found in possession of six suspects and a ransom letter left by person who stole a Christmas tree.Students analyzed the evidence by studying the black ink in six different pens vs. the black ink sample found on the ransom letter. The students already were clued into what Chromatography was because they learned to how to breakdown the term. They were involved in “the process of recording color,” more specifically by separating components of the black ink samples, into two phases, stationary to mobile phases, and then compare the results against the black ink sample of the ransom letter.

Students adding black ink samples of six pens to the chromatography paper.

Chromatography paper is a powerful analytical tool. Students added the six ink samples to the paper. They allowed the paper to slowly absorb water, which in turn took the station ink sample and the ink sample and allowed it to move through the fibers of the paper into its mobile phase. This process separated the ink substance which is a low-molecular-mass and move it between its stationary phase and mobile phase.

chromatography results

Student C.S.I. lab sample comparison of ransom letter and six black ink samples collected.

The results were very conclusive and turned over to the Pickaway County’s Sheriffs Department to further inform their investigation of who stole the Christmas tree case.