CH.8 Nucleotides Nucleic
Acids (2) questions fully
solved & updated(100%
accuracy)
Why is it so unlikely that purine would ever pair with purine? - answer
What types of forces help to stabilize DNA structure in addition to the
phosphodiester bonds of the backbone and the hydrogen bonds between
base pairs? - answer bases are mostly planar and relatively hydrophobic
so they tend to stack parallel to one another through van der Waals and
dipole-dipole interactions
--> this minimizes base contact with water and helps stabilize 3-D
structure
What is the primary structure of nucleic acids? - answer primary structure
is the covalent structure (the sequence of nucleotides)
What is the secondary structure of nucleic acids? - answer secondary
structure is the regular, stable structure
What is the tertiary structure of nucleic acids? - answer tertiary structure
is the folding of nucleic acid into chromatins or nucleoids
How do strands of nucleic acids come to be associated with each other? -
answer H-bonding between bases allows for the association of 2 or 3
strands of nucleic acids
, Why is DNA preferred over RNA for retaining our genetic information? -
answer DNA is alkali stable (yet susceptible to acid) while RNA is
somewhat acid-stable (but susceptible to base)
the cell is usually slightly basic with a pH of ≈7.4 and thus DNA the more
suitable nucleic acid
What are Chargaff's Rules for DNA? - answer 1. base composition of DNA
varies between species
2. different tissues from the same species have the same DNA composition
3. base composition does not change with age, environment, etc.
4. sum of purines = sum of pyrimidines
i.e. A + G = T + C --> arises from A-T preferred base pairing and G-C
preferred base pairing
What is the preferred secondary structure of DNA? - answer preferred 2°
DNA structure results from two complemetary DNA strands H-bonding
between their bases in an antiparallel orientation
What consequence does the antiparallel orientation have on DNA
structure? - answer antiparallel orientation allows bases to adopt Watson-
Crick pairs
permits bases on same strand to stack
What consequence does the hydrogen-bonding between base pairs have
on DNA structure? - answer with bases H-bonding to one another, the
sugar-phosphate backbone forms a helical structure outside
What functional benefit comes with a helical structure in DNA? - answer
helical conformation minimizes base (hydroPHOBIC portion) exposure to
water and maximizes sugar-phosphate (hydroPHILIC portion) exposure to
water
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