DNA structure

Question 1

Nucelosides

Answer 1

-Lack the phsophorisphoric acid

Question 2

Nucleotides

Answer 2

-Contain phosphoric acid attached to the sugar via a phosphodiester bond

Question 3

what are Chargaff’s Rules

Answer 3

1- G=C; and A=T
2-The DNA composition is the same in all cells of the same species
3-
4-

Question 4

What are the two forces that hold DNA strands together?

Answer 4

-Entropy, and Ring/base stacking, (Hydrogen important for specificity because you cannot bond with acceptor and acceptor

Question 5

Why is base stacking important?

Answer 5

• Minimizes the unfavorable contact of the bases with water
• Creates favorable π−π interactions in which the electrons are shared between p-orbitals of adjacent base pairs
• The stacking of GC base pairs with their neighbors contributes more to DNA stability than does AT base pair stacking.

Question 6

What is the hyperchromic effect?

Answer 6

-The increase in absorbance of light of a substance. (The single stranded DNA absorbances more due to the exposed nitrogenous bases.)

Question 7

What happens when you add salt to DNA? would Tm be higher or lower

Answer 7

-The salt will interact with the phosphate backbone and stabilize the structure lowering Tm.

Question 8

How do proteins recognize sites to replicate?

Answer 8

• Major grooves have more specific “information” through chemical and base interactions that can distinguish T:A, A:T, G:C, and C:G.
• Palindromes