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BCCB2000 Biochem Exam Latest Update
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BCCB2000 Biochem Exam LatestUpdate
RNA doesn't usually exist as a double helix, like DNA, but you would expect some
secondary structure to form because: - Answer The hydrophobic bases would try to
minimise their contact with water. Phosphodiester backbone would try to maximise its
contact with water
Thymine is not normally present in RNA
Guanine does not normall base pair with uracil in RNA
The nucleotide sequence has little or no effect on which form (A, B, or Z) DNA will take. -
Answer False. The Z form can be found in GC rich regions
Nucleotide sequence has little or no effect on which form DNA takes. T/F - Answer False
Which of the following could be components of guanylate: - Answer phosphate,
guanosine, guanine
The base pair Adenine-Thymine (A-T) has _____ hydrogen bonds within the structure of
DNA - Answer 2
The two pyrimidines found in RNA are_____________and _____________ - Answer uracil,
cytosine
Guanine and cytosine base pairs share three hydrogen bonds. T/F - Answer true
By definition, the 5' end of a DNA or RNA strand: - Answer has no nucleotide attached to
the 5' hydroxyl
The two pyrimidines found in DNA are_____________and _____________ - Answer thymine
and cytosine
When double-stranded DNA is heated at neutral pH, which change does not occur? -
Answer The covalent N-glycosidic bond between the base and the pentose breaks
The A-form of DNA predominates in dehydrated conditions; The B-form of DNA
predominates in aqueous solution. T/F - Answer True
There are estimated to be about 10^13 cells in the human body (not counting bacteria).
Estimate the length of DNA from all cells in the human body assuming that all cells are
diploid (i.e.23 pairs of chromosomes) and that all of the DNA is in the B-form. - Answer
2.0 x 1013 m. That is about 70 trips from the earth to the sun and back
, Nucleic acid samples have been isolated from four different organisms. The nucleic
acids have the following composition (%):
Sample 1: A=30; T=18; U=0; G=21; C=33
Sample 2: A=30; T=0; U=18; G=21; C=33
Sample 3: A=18; T=18; U=0; G=32; C=32
Sample 4: A=18; T=0; U=18; G=32; C=32
Which DNA sample would be expected to have the highest Tm (melting point)? - Answer
Sample 3. A=18; T=18; U=0; G=32; C=32
Which of the following could be components of uridylate: - Answer ribose, phosphate,
uridine, uracil
Which of the following descriptions applies to the B-form of DNA? - Answer
right-handed, long and thin, 3.32 A and 10 bp per turn. Usual in vivo conformation
The phosphodiester bonds that link adjacent nucleotides join: - Answer the 3' hydroxyl
of one nucleotide to the 5' hydroxyl of the next nucleotide
Purines and pyrimidine bases in DNA are molecules that have: - Answer both hydrogen
bond acceptors and donors; intermolecular hydrogen bonds
In a double-stranded nucleic acid, cytosine typically base-pairs with: - Answer guanine
Two molecules of double-stranded DNA are the same length (1000 base pairs) but differ
in their base composition. Molecule 1 contains 20% A+T and molecule 2 contains 60%
A+T. Consequently, molecule [a] has a higher Tm (melting point). - Answer 1. Molecule 1
has 20% A+T which means there must be 80% G+C. Melting point is determined by the
amount of G+C relative to A+T in the ratio: A+T/G+C. The lower the ratio the greater the
G+C content and the higher the Tm (melting point).
Molecule 1: 20/80 = 0.25
Molecule 2: 60/40 = 1.5
Which of following interactions are the likely result of the stacking of base pairs in DNA?
- Answer pi-pi, dipole-dipole, hydrophobic, dispersion
Two purines found in DNA are_____________and _____________ - Answer guanine and
adenine
In double-stranded DNA: - Answer the two strands have complementary sequences
The stacking of hydrophobic bases in DNA has the advantage that it [a] their contact
with water and [b] the DNA structure. - Answer minimises, stabilises
Which of the following deoxyoligonucleotides will hybridize with a DNA containing the
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