26Dna Structure ReplicationHard1 mark
The scientist Erwin Chargaff analysed the base composition of the DNA of several species. The table shows some of Chargaff’s data.
| species | adenine | guanine | cytosine | thymine |
|---|---|---|---|---|
| E.coli | 24.7 | 26.0 | 25.7 | 23.6 |
| maize | 26.8 | 22.8 | 23.2 | 27.2 |
| grasshopper | 29.3 | 20.5 | 20.7 | 29.3 |
| sea urchin | 32.8 | 17.7 | 17.3 | 32.1 |
| octopus | 33.2 | 17.6 | 17.6 | 31.6 |
| rat | 28.6 | 21.4 | 20.5 | 28.4 |
Which statements can be concluded using only the data in the table?
- 1Cytosine binds to guanine using three hydrogen bonds.
- 2Approximately 50% of the bases in any of the species are either adenine or thymine.
- 3The base composition of DNA varies between different species.
- 4The number of cytosine bases in any of the species is approximately the same as the number of guanine bases.