Nucleic Acids and the RNA World Flashcards
If you have a polymer with 10 A bases followed by 10 C bases and the strand bonds to another strand with 20 T bases, how would the stand be different than normal?
The width of the DNA double helix would vary along the length of the strand
Which carbon does the phosphate group bond to on the sugar?
5
Which carbon does the nitrogenous base bond to on the sugar?
1
Why does G not pair with T and A pair with C?
They cannot form as many hydrogen bonds as A-T and G-C pairs
What is the structural feature that allows DNA to replicate?
Complimentary pairing between the nitrogeneous bases
RNA world hypothesis
RNA both stored genetic information and catalyzed its own replication
3 components of a nucleotide
- phosphate group
- 5 carbon sugar
- nitrogenous base
What is the central component of the nucleotide?
sugar
Difference between ribose and deoxyribose
Deoxyribose contains one less oxygen on its 2 position of the sugar
this hydroxide on the 2 of ribose makes it much more reactive and less stable
Purines
adenine and guanine
both contain 9 rings (larger)
Pyrimindines
cytosine, uracil, thymine
contain 6 rings
How do nucleotides polymerize?
Via condensation
reactions between hydroxyl on the sugar of one nucleotide and phosphate on another nucleotide
What does the condensation reaction create?
Phosphodiester linkage (covalent)
H20 is released
5’ end
contains an unlinked 5’ phosphate
3’ end
contains an unlinked 3’ hydroxyl (sugar)
Which end are nucleotides added to in growing chain?
3’ end
this makes sense because the 3’ end contains the central sugar from which things are attatched
Why is polymerization not spontaneous?
It requires an input of energy
How is polymerization catalyzed?
the creation of activated nucleotides (ATP)
3 phosphates are all negatively charge and thus they have a strong repel force
What is the backbone of nucleic acids?
Sugar-phosphate backbone
What did Franklin and Wilkins tell us?
showed that the pattern of the molecule was probably helical
Chargaff’s rule
the number of purines in a given molecule is equal to the number of pyrimidines
What type of bonds form between nitrogenous bases?
Hydrogen
Antiparallel
two strands of DNA must be oriented in opposite directions
What do the negatively charged phosphates make DNA?
Hydrophillic overall
DNA grooves
allow proteins to bind
What makes DNA twist?
hydrophobic interactions
vander der Waals interactions
Tertiary structure of DNA
normally wraps around proteins called histones
DNA copying steps
NEED TO LEARN
paradox of DNA
its orderliness and stability makes it great at storing information but also make it a bad catalysis
therefore, RNA is preferred to be the first self-replicating molecule
How is secondary structure of RNA different?
It folds with the same strand
it does not have a complementary strand
Hairpin
this occurs in the loop of RNA where there are unpaired bases because of the single strand secondary structure of Rna
RNA’s versatility
RNA can fold into many 3D shapes, which makes it more versatile than DNA
Ribozymes
RNA enzymes that help catalyze reactions
similar to protein enzymes
