Nucleotides, DNA and RNA Flashcards
What are the two nucleic acid bases?
Pyramidines
Purines
What are the base factors of pyrimidines?
Cytosine-C
Thymine-T
Uracil-U
**Can be a single six ring structure
What are the base factors of purines?
Adenine-A
Guanine-G
**Can be a double ring structure
What are the derivatives of pyrimidine/purine bases?
Nitrogen-containing heteroaromatic molecules
- They are planar or almost planar
-Absorb UV light around 250nm.
What is the difference between Thymine and Uracil?
Thymine is a DNA base whereas Uracil is an RNA base.
What is the difference between deoxyribose and ribose?
At the 2nd Carbon there is hydrogen on deoxyribose and a hydroxide on ribose.
What is the pentose sugar ring attached to in nucleotides?
Nitrogenous base via a N-glycosidic bond.
Where is the N-glycosidic bond formed in pyramidines and purines?
The bond is formed to position N1 in pyrimidines and to position N9 in purines.
Describe the stability of the N-glycosidic bond?
This bond is quite stable toward hydrolysis, especially in pyrimidines.
What is the N-glycosidic bond cleavage catalsysed by?
Acid.
What kind of rotation does the N-glycosidic bond have?
Free rotation can occur around the g-glycosidic bond in free nucleosides and nucleotides.
Anticonformation is found in normal _-___
B-DNA
What do nucleotides consist of?
Nitrogenous base+pentose sugar=nucleoside
nucleoside+phosphate group=nucleotide.
How do you distinguish between the carbon atoms of the pentose and of the nitrogenous base?
Carbons of the pentose are designated N’ to alleviate confusion.
What is chargaff’s rule?
In a DNA double strand, every A is paired with a T(every T with an A)
In a DNA double strand, every G is paired with a C(C with a G)
What is the conclusion from chargaff’s rule?
Any DNA double strand which follows the base-pairing rules must have equal amounts of A and T, and equal amounts of G and C.
BALANCED
What happens as a result of the polymerisation process?
the 5’ carbon and 3’ hydroxyl groups of the sugar in each repeating unit are connected by phosphate groups.
What does forming polymers involve?
Condensation
The energy for the polymerisation process comes from the _________of the ________________group
hydrolysis
triophosphate
Which base has do RNA and DNA have: Uracil or Thylamine
RNA: Uracil
DNA: Thymine
Which way is a DNA strand read?
5’ to 3’ for the bases.
How many hydrogen bonds connect pairs of bases?
AT pair has 2 hydrogen bonds.
GC base pair has 3 hydrogen bonds.
Describe the arrangement of hydrogen bonds in relation to equidistant nucleotides?
The edges of the nucleotides are kept apart by the same distance, the DNA backbones are arranged EXACTLY PARALLEL in space.
Bases are arranged exactly ________ to each other.
Parallel.
Describe the arrangement of DNA in a helix?
Complementary
Antiparallel
Paired strands
Twist into a helical
confirmation
How is a complementary DNA strand read?
3’ 5’ base
How do nucleotides attach to each other in the DNA strand by?
Phosphodiester bonds.
bonded from 3’ to 5’
Are T and C purine or pyrimidine?
Pyrimidine
Are G and A purine or pyrimidine?
Purine.
How long is each turn of the helix in base pairs?
10 base pairs
(10.4)
What stacking stabilises the helix structure?
The stacking of the the bases.
What is a pi-pi interaction in the DNA helix?
When the aromatic ring of a base stacks next to another and they share their electron probabilities.
What do the major and minor groove do in the DNA helix?
Act as base pair recognition and binding sites for proteins
What does the major groove contain?
base pair specific information
What does the minor groove contain?
Base pair non-specific information.
What is the choice of DNA form dependent on?
-Sequence
-Ionic conditions
-Temperature
How can DNA double strands be seperated?
By heating or through the action of energy-expending enzymes.
What is brownian motion?
Higher temperature, more movement of atoms in liquid and gases.
Do DNA double strands stay together or separated by temperature above melting point?
Hydrogen bonds severed.
Melted into two strands.
Does annealing occur in cold or heated temperatures?
Cold
**base pairing is annealing
DNA denaturation is commonly monitored by UV spectrophotometry at ___ nm.
260nm
How do complementary pieces of single-stranded DNA (ssDNA) will form spontaneous double strands in solution?
Because their sequences match to allow base-pairing.
What is the major reason for the differences between organisms?
Differences in the genomic DNA sequence.
