S4.2.2 For the adult
The structure of DNA
DNA is a code with only four letters. How can four letters hold the instructions for a whole body?
What this chapter teaches
DNA is a double helix. Each strand has a sugar and phosphate backbone with a base on each sugar. A pairs with T and C pairs with G, so one strand tells you the other, and this is how a cell copies its DNA. Three bases code for one amino acid.
Three questions to ask
There is no one right wording. Listen for the idea.
- If one strand of DNA reads GGATC, what does the other strand read?
- Why are the two strands of DNA partners and not copies?
- How does a cell use the pairing rule when it copies its DNA?
After the chapter, the learner can
- Describe DNA as a double helix with paired bases
- Pair A with T and C with G to complete a strand
What they copy into their notebook
DNA is a double helix. Sugar and phosphate make each backbone. The rungs are base pairs: A with T, C with G. Three bases code for one amino acid.