We have just finished Microbe studies and together we have chosen to look at Inheritance and Genetics next. Again, I will be using the Edexcel IGCSE specification as guidance. Our studies will hopefully be in-depth and very hands on before we settle down to answering past exam papers to test how much the children understand.
Genetics and Inheritance
To introduce this incredibly exciting topic, I used the following video. I really recommend it as a starting point. It is very powerful.
This lesson was based on 3.13 to 3.15 of the specification which focuses on DNA. I really wanted to play around a lot with this, as an understanding of the building blocks of the chromosomal material is essential to grasping meiosis, mitosis, mutations and the like.
Revision of the cell and its nucleus
We had completed a unit on the cell a couple of years ago when we made a jelly cell and a play dough cell:
They each had a quick read of the post to refresh their memories and then I asked where inside the cell were the chromosomes located, to which they correctly answered the nucleus:
The Chromosome
I showed them some pictures of chromosomes, and we made up a quick cell using a hoola hoop and pipe cleaners for the nucleus and the chromosomes. I did this so they could physically make some chromosomes themselves and place them inside the nuclear membrane:
Together we labelled them:
I had to laugh when after the morning meeting, whilst reading about Watson and Crick and the history of Genetics L12 brought me her latest loom band creation. A chromosome!
I had photocopied this chart which shows the unraveling of the chromosome into first the genes and then further into the DNA strands:
I mentioned, but didn’t go into too much depth, that each gene coded for a specific protein, that is each gene contained the recipe for a specific protein. These proteins are essential for our body to function as it is meant to. The proteins are involved in every aspect including, but not limited to, digestion, motion, circulation and immunity. We would be learning more about this coding in a future lesson.
Using the chart above allowed the children to be able to visualise exactly how a chromosome is made up. I also found a YouTube video which explains it all brilliantly:
This video may need to be previewed as it hints at evolution which some may not want their children exposed to. However it is not explicit and is brushed over very quickly. After watching the above video we were ready to move on to learning about DNA in greater depth.
The Double Helix DNA Strand
This video explains brilliantly what DNA is and what it does:
And this one is a great animation of the same but with a little more information:
Crick and Watson Scientist study
We had already carried out a study of Crick and Watson during which we had built three DNA molecules from different kits we own:
This was fantastic but the children could easily have just followed the instructions given in the kits without really understanding what they were building.
I have found one of the most important ways the children internalise the information they are learning is to design and build a model themselves to demonstrate their learning. When they are able to build and consequently explain their own model to me in-depth, I know they have learnt and understood that which they need to.
Designing and building their own models
We read this book which gives some fabulous drawings of the double helix:
The DNA molecule is two phosphate strands coiled to form a double helix and linked together by a series of paired bases: adenine (A), with thymine (T) and cytosine (C) with guanine (G) (from specification noted above).
I used the idea of a puzzle to show how the four bases fit together and why they had to be specifically paired to their corresponding half and could not be fit together with any of the others. To illustrate this I used some paired phonics puzzles:
I turned over and coloured in four different colours and labeled them with the letters of the four bases – Guanine, Adenine, Cytosine and Thymine:
I had the children play about with them and they quickly saw that the C and G fit together (the Car goes into the Garage) and the A and T fit together (the Apples are found in the Tree). They tried other combinations and found that these were the only combinations which fit:
A would only fit with T, whilst C would only fit with G.
With this in mind I gave them a selection of paper clips, straws and pipe cleaners with which to work. There are many ways out there to do this activity using sweeties, or beads. I used what we had on hand:
They all did really well and included a key as well to explain what each item they used would represent:
C12:
L12. L had some difficulty with hers which really highlighted a lack of understanding. Having the children create what they learn really does highlight areas they are struggling to understand. She did a beautiful job after a bit of explaining:
T12:
Extracting DNA Samples
Before we had a go at extracting our own samples of DNA we took a look at this video which explains why and how it is done properly for identification and forensics. The video is interactive and allows you to extract the DNA yourself, virtually. After they had played about with the video for as long as they wanted, we did our own rather crude extraction.
Each child had a go at extracting DNA from either a banana, a tomato or themselves. I wrote a post about how we extracted DNA samples yesterday:
Viewing DNA under the microscope
I had bought some slides of organelles for the children to look at under the microscope. I bought them from Amazon. This time we looked only at the DNA:
I also encourage the children to make their own slides using the DNA we had extracted previously. Even if they were not successful it would still be great lab practice in preparing their own slides:
First they carefully pulled some DNA clumps out of the solution and placed them in the middle of the slide:
Next they placed a cover over the DNA, pressing it gently to get rid of air bubbles. The slide is now ready to look at under the microscope:
During our next schooling week we will be looking at Chromosomes in greater detail as well as their replication and mutation.
