We have looked quite extensively at the structure of DNA as well as carrying out a study on the scientists who first discovered its structure and making our own models:
The next thing the children needed to know about was DNA replication. This would be fairly important for their cell division lessons on Mitosis and Meiosis as the first stage of both includes the DNA replicating itself prior to cell division.
As you can see from above the DNA strand is made up of two strands joined together as a double helix by paired bases. Before a cell divides its chromosomes needs to be replicated exactly. This occurs by the two stranded DNA molecule ‘unzipping’, thus separating the double helix into two separate strands:
As they separate free nucleotides lock onto the bases, forming new strands. the new, exact copies of DNA are thus formed as shown above. GCSE bitesize have a great little animation showing this which the children viewed until they felt they fully understood. The video can be accessed here.
I also had them watch another animation. It was more advanced than the children needed but I still felt there was value in watching it:
We also watched the following video. I liked this one more because I felt the animation was a little more realistic and less simplified whereas the audio and explanations were easier to understand with less information:
In order to check the children understood what they had learnt we used one of the models they had already made. I printed out the three very simplified stages I wanted them to know onto card. Their task was to illustrate these stages using their model:
- The DNA spiral unzips:
- Free nucleotides lock onto the bases:
- Two copies of the original DNA spiral is formed:
This was a fairly quick and simple lesson, but was nonetheless important knowledge to possess ahead of our next two lessons on cell divisions – mitosis and meiosis.