DNA Strands in Strawberries

Sisters4Science is back at Joslin after many icy snow days.  We have waited for spring, but Mr. Winter seems to love staying in Chicago as long as he wants to.  However this winter storm can’t stop us having fun in hands-on science experiments.  We welcomed Ms. Charlene, an amazing marine-biologist.  She has been with Sisters4Science over the last five years so it was like “reunion” time for her and a few senior girls!  She brought fresh strawberries to ignite our fun part of science.

Since we had some new girls who have been recently recruited, we had a time to introduce ourselves before we got into the fun activity.  Ms. Charlene introduced herself first then threw out a warm-up question; “What is your favorite toothpaste?”  The girls absolutely loved answering this question.

Ms. Charlene began her lesson by activating background knowledge questions: “What is DNA?”  “Anyone knows where our DNA is located?” The girls were so excited responding her questions.  “It’s the characteristics of a person or a plant.”  “It’s in a cell.”  “It’s right there,” pointing on the Ms. Charlene’s drawing on the board.  It was so wonderful seeing their excitement to what they already knew.  The girls were very confident in responding all Ms. Charlene’s questions!  Here was a little higher level of question continued: “Do we, human being, have a cell wall?”  The girls were little hesitant answering this, but one girl said, “Only plants have a cell wall. Animals don’t have.”  “Yes, only plants have a cell wall,” responded Ms. Charlene.  “What about strawberries then?” she asked again. The girls said in unison, “They have a cell wall; it’s a plant.”  The girls quickly understood where we were going towards with the strawberries.

Joslin3“Now, we need to break the cell walls in strawberries. So first have three or four strawberries in a zip-block bag then smash them,” explained Ms. Charlene.  The girls very much enjoyed knocking on the strawberries.  Once we made “mashed strawberries, it was time to filter it through the cotton gauze like making a strawberry smoothie.  “What do you think we need to break the cell walls?” asked Ms. Charlene.  “Do you see anything from the materials we have?”  “I see salt and an alcohol-like bottle.”  “Yes, we need a pinch of salt and stir gently to break the cell walls. Let’s have a pinch of salt in it,” clearly explained Ms. Charlene, guiding through the next step.  Then, Ms. Charlene added a little bit of ethanol into each strawberry smoothie.  Here it came, DNA strings!  The girls were like “Wow.”  For most girls, it was their first time to see DNA strings right before their eyes, even they did all the work to extract DNA from the fresh strawberries! It was such a “Wow” day for all of us!