Properties of the DNA double helix Flashcards
What do ssDNA and dsDNA mean?
single stranded DNA; double stranded DNA
What two numbers were of particular interest in Franklin and Wilkins’ experiments? What did they mean?
3.4 nm and 0.34 nm.
3.4 nm = distance per one helical turn
0.34 nm = distance between adjacent base pairs
How many base-pairs in one turn of the DNA double helix?
3.4 nm in one turn/0.34 nm between base pairs = 10 base pairs/turn
What is the diameter of the double helix?
2 nm (distance between C1’ bonds = 1.085 nm)
How is the DNA helix oriented?
Right-hand helix
List the 3 variants of dsDNA.
A-DNA, B-DNA and Z-DNA
Which variant of dsDNA are we concerned with? Why?
B-DNA occurs in physiological conditions.
What is the angle of rotation between base pairs?
36 degrees
What is the angle of the major groove? The minor groove?
Major: 257 degrees
Minor: 103 degrees
What is the importance of the major and minor grooves?
Different nucleotide shapes are exposed, allowing this information to be accessed by proteins without unwinding the DNA.
List some differences between DNA and RNA.
Uracil instead of thymine
Ribose instead of deoxyribose
RNA is single-stranded
For the most part, RNA is not used for storing genetic information
Some RNA has catalytic activity
How can DNA form secondary structures?
Base pairs within one strand can bind together. Different strands can also bond with each other, but bonding within one strand is easier and thus more common.
Which is more reactive, DNA or RNA? Why?
RNA because of the 2’ OH of the ribose sugar.
