Experiences

DNA - The hereditary substance

Ewelina Gizińska

Poland

Primary school

Biology, Science

Laboratory, Extracurricular activity

Direct

Problem: Terms such as DNA, genes are familiar even to children in primary school. The curriculum does not address the teaching of this topic, but ambitious and willing person can enter the world of genetics at this stage of education. But how to do it in an interesting and accessible way for kids?

Solving the problem: I suggest to carry out additional activities in genetics, in which students learn basic information about the hereditary substance called DNA, and will have the opportunity to isolate and see the strands of fruit and vegetable DNA with the help of well-known method, using reagents available in every kitchen.
Conducting the classes:
Basics of genetics
The teacher explains what DNA is, where it is located in the cells and what for responsible is. Teacher moderates a talk with students aiming to foster curiosity of subject of classes. Teacher asks questions, and students are trying to find answers:
What are the qualities we inherit from our parents?
How does each tiny cell could contain 2 meters of DNA chain?
Do plants also have genetic material?
What for do scientists isolate DNA from cells?

Isolation of DNA from fruit and vegetables
Students with the help of teacher perform the following experience.
Pour about 100 ml of water to the beaker, add a teaspoon of dishwashing liquid and 2 teaspoons of salt, then mix.
Cut half a tomato (or other vegetable or fruit) into smaller pieces and mix (a few seconds) using a blender.
Add the mixture and salt to pieces of tomato.
Put the beaker with a mixture for about 15 minutes in the water of a temperature about 60˚ C, then move in a dish with ice or cold water for 5 to 10 minutes to cool it.
Then pour the tomato mixture through a coffee filter.
Pour the collected filtrate into a test tube and add to it a small amount of concentrated, cold ethyl alcohol (from the freezer), gently pouring the walls.
DNA precipitates from the solution in the form of visible threads and lint (accompanied by air bubbles).

The role of the various stages of DNA isolation:
mixing - mechanically destroys the cell walls
salt and dishwashing liquid (detergent) - break down cell and nuclear membranes, in which DNA is hidden
incubation at 60 ˚ C - accelerates the disintegration of membranes and destroys the DNA -degrading enzymes
filtering – enables the separation of cellular debris from the solution (filtrate), which contains the DNA
ethanol - causes that dissolved DNA is precipitated from the solution and is visible in the form of threads.