DNA structure Flashcards
What function do minor and major grooves have? [1 mark]
Receptors for drugs
A form of DNA structure [3 marks]
- Right handed helix
- Compact
- Similar major and minor grooves
B form of DNA structure [3 marks]
- Right handed helix
- 10 base pairs per turn
- Most common form in cells
Z form of DNA structure and function [3 marks]
- Alternating purine/pyrimidine base sequence
- Found in nucleus
- Might control gene expression
What is an example of an A form helix? [1 mark]
tRNA
How many hydrogen bonds does cytosine and guanine form? [1 mark]
3
How many hydrogen bonds does thymine and adenine form? [1 mark]
2
What happens in a Holliday junction? [2 marks]
- Four stranded junction of complementary DNA
- DNA exchange occurs
What is the primary DNA structure? [1 mark]
The sequence of bases
What is the secondary DNA structure? [1 mark]
Helical structure
How can the secondary DNA structure be seen? [2 marks]
- X-ray
- Chemistry
What is the tertiary DNA structure? [1 mark]
DNA supercoiling
How can the tertiary DNA structure be seen? [1 mark]
Electron microscopy
What is the quaternary DNA structure? [1 mark]
Interlocked chromsomes (needs to be untangled)
E. coli DNA structure [3 marks]
- Circular DNA
- Supercoiled (with DNA gyrase)
- ~50 independently supercoiled domains
