Biochemistry Test 4 [Chpt 8]
Which of the following are possible base compositions for single-stranded RNA?
%A %G %C %T %U 5 45 45 0 5 25 25 25 0 25 35 10 30 0 25
Based on Chargaff's rules, which of the following are possible base compositions for double-stranded DNA?
%A %G %C %T %U 5 45 45 5 0
Which of the following deoxyoligonucleotides will hybridize with a DNA containing the sequence (5')AGACTGGTC(3')?
(5')GACCAGTCT(3')
The ribonucleotide polymer (5')GTGATCAAGC(3') could only form a double-stranded structure with:
(5')GCTTGATCAC(3').
Xeroderma Pigmentosum
A disease that has increased sensitivity to the sun and increased risk of cancer & sunburn because the DNA repair system does not work.
How are a nucleoside and a nucleotide similar and how are they different?
Both have a nitrogenous base and a pentose but nucleotides also have a phosphate group, which nucleoside lacks.
In living cells, nucleotides and their derivatives can serve as:
Carriers of metabolic energy, coenzyme factors, intracellular signals, and precursors for nucleic acid synthesis.
Triple-helical DNA structures can result from Hoogsteen (non Watson-Crick) interactions. These interactions are primarily:
hydrogen bonds involving the bases.
Chargaff's rules state that in typical DNA:
A + G = T + C.
Purines have ____ ring(s), (each) containing _____ nitrogen(s), whereas pyrimidines have _____ ring(s), (each) containing _____ nitrogens.
2; 2; 1; 2
The alkaline hydrolysis of RNA does not produce:
3',5'-cAMP.
Which of the following is not true of all naturally occurring DNA?
The ratio A+T/G+C is constant for all natural DNAs.
Which of the following is a palindromic sequence?
GGATCC CCTAGG
Why does lowering the ionic strength of a solution of double-stranded DNA permit the DNA to denature more readily (for example, to denature at a lower temperature than at a higher ionic strength)?
Lowering ionic strength reduces the screening of negative charges on the phosphate groups by positive ions in the medium. Resulting in a stronger charge-charge repulsion between the phosphate, favoring strand separation.
In comparison with DNA-DNA double helices, the stability of DNA-RNA and RNA-RNA helices is:
RNA-RNA > DNA-RNA > DNA-DNA.
When double-stranded DNA is heated at neutral pH, which change does not occur?
The covalent N-glycosidic bond between the base and the pentose breaks.
In the Watson-Crick model for the DNA double helix (B form) the A-T and G-C base pairs share which one of the following properties?
The distance between the two glycosidic (base-sugar) bonds is the same in both base pairs, within a few tenths of an angstrom
Which of the following statements concerning the tautomeric forms of bases such as uracil is correct?
The lactam form predominates at neutral pH.
Which one of the following is true of the pentoses found in nucleic acids?
The pentoses are always in the Beta-furanose forms.
In the Watson-Crick model for the DNA double helix, which of the following is not true?
There are two equally sized grooves that run up the sides of the helix.
The difference between a ribonucleotide and a deoxyribonucleotide is:
a deoxyribonucleotide has an —H instead of an —OH at C-2.
In the Watson-Crick structure of DNA, the:
absence of 2'-hydroxyl groups allows bases to lie perpendicular to the helical axis.
The compound that consists of ribose linked by an N-glycosidic bond to N-9 of adenine is:
adenosine
The nucleic acid bases:
are roughly planar.
The phosphodiester bond that joins adjacent nucleotides in DNA:
associates ionically with metal ions, polyamines, and proteins.
Double-stranded regions of RNA:
can form between two self-complementary regions of the same single strand of RNA.
Compounds that generate nitrous acid (such as nitrites, nitrates, and nitrosamines) change DNA molecules by:
deamination of bases.
The experiment of Avery, MacLeod, and McCarty in which nonvirulent bacteria were made virulent by transformation was significant because it showed that:
genes are composed of DNA only.
In a double-stranded nucleic acid, cytosine typically base-pairs with:
guanine
The DNA oligonucleotide abbreviated pATCGAC:
has a hydroxyl at its 3' end.
The phosphodiester bonds that link adjacent nucleotides in both RNA and DNA:
join the 3' hydroxyl of one nucleotide to the 5' hydroxyl of the next.
The double helix of DNA in the B-form is stabilized by:
nonspecific base-stacking interaction between two adjacent bases in the same strand.
In the laboratory, several factors are known to cause alteration of the chemical structure of DNA. The factor(s) likely to be important in a living cell is (are):
oxygen, and UV light.
The "energy carrier" ATP is an example of a(n):
ribonucleoside triphosphate
B-form DNA in vivo is a ________-handed helix, _____ Å in diameter, with a rise of ____ Å per base pair.
right; 20; 3.4
In nucleotides and nucleic acids, syn and anti conformations relate to:
rotation around the sugar-base bond.
In the Watson-Crick model of DNA structure (now called B-form DNA):
the bases occupy the interior of the helix.
In the Watson-Crick model of DNA structure:
the distance between two adjacent bases in one strand is about 3.4 Å.
For the oligoribonucleotide pACGUAC:
the nucleotide at the 5' end has a phosphate on its 5' hydroxyl.
In the chemical synthesis of DNA
the nucleotide initially attached to the silica gel support will become the 3' end of the finished product.
In DNA sequencing by the Sanger (dideoxy) method:
the role of the dideoxy CTP is to occasionally terminate enzymatic synthesis of DNA where Gs occur in the template strands.
In double-stranded DNA:
the two strands have complementary sequences.
A major component of RNA but not of DNA is:
uracil
