Question 1

Describe qualitatively how the tm for a double-stranded DNA depends on its nucleotide composition.

Accepted Answer

In general,the higher the proportion of G and C,the higher the melting temperature,t_m.More thermal energy is required to break the three hydrogen bonds holding G$ \equiv$C pairs than to break the two hydrogen bonds holding A=T pairs.Also,G$ \equiv$C pairs stack better than A=T pairs,thereby stabilizing the double helix better.

Question 2

Match the type of bond with the role below:
-

Accepted Answer

b
a
d
c

Question 3

For the oligoribonucleotide pACGUAC:

Accepted Answer

A) the nucleotide at the 3' end has a phosphate at its 3' hydroxyl. 
B) the nucleotide at the 3' end is a purine. 
C) the nucleotide at the 5' end has a 5' hydroxyl. 
D) the nucleotide at the 5' end has a phosphate on its 5' hydroxyl. 
E) the nucleotide at the 5' end is a pyrimidine. 
A) the nucleotide at the 3' end has a phosphate at its 3' hydroxyl. 
B) the nucleotide at the 3' end is a purine. 
C) the nucleotide at the 5' end has a 5' hydroxyl. 
D) the nucleotide at the 5' end has a phosphate on its 5' hydroxyl. 
E) the nucleotide at the 5' end is a pyrimidine. D

Question 4

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):

Accepted Answer

A) heat. 
B) low pH. 
C) oxygen. 
D) UV light. 
E) both C and D. 
A) heat. 
B) low pH. 
C) oxygen. 
D) UV light. 
E) both C and D.

Question 5

When double-stranded DNA is heated at neutral pH,which change does not occur?

Accepted Answer

A) The absorption of ultraviolet (260 nm)light increases. 
B) The covalent N-glycosidic bond between the base and the pentose breaks. 
C) The helical structure unwinds. 
D) The hydrogen bonds between A and T break. 
E) The viscosity of the solution decreases. 
A) The absorption of ultraviolet (260 nm)light increases. 
B) The covalent N-glycosidic bond between the base and the pentose breaks. 
C) The helical structure unwinds. 
D) The hydrogen bonds between A and T break. 
E) The viscosity of the solution decreases.

Question 6

Which of the following are possible base compositions for single-stranded RNA?

Accepted Answer

The answer of Which of the following are possible base...

Question 7

Which one of the following is true of the pentoses found in nucleic acids?

Accepted Answer

A) C-5 and C-1 of the pentose are joined to phosphate groups. 
B) The pentoses are in a planar configuration. 
C) The bond that joins nitrogenous bases to pentoses is an O-glycosidic bond. 
D) The pentoses are always in the $\beta$-furanose forms. 
E) The straight-chain and ring forms undergo constant interconversion. 
A) C-5 and C-1 of the pentose are joined to phosphate groups. 
B) The pentoses are in a planar configuration. 
C) The bond that joins nitrogenous bases to pentoses is an O-glycosidic bond. 
D) The pentoses are always in the $\beta$-furanose forms. 
E) The straight-chain and ring forms undergo constant interconversion.

Question 8

For the helix in double-stranded B-form DNA,the majority of the stability can be attributed to:

Accepted Answer

A) base-pairing interactions via H-bonds. 
B) interactions along the phosphate backbone. 
C) base-stacking interactions via van-der-Waals interactions. 
D) covalent bonds between adjacent bases in one strand. 
E) ionic interactions with metal ions. 
A) base-pairing interactions via H-bonds. 
B) interactions along the phosphate backbone. 
C) base-stacking interactions via van-der-Waals interactions. 
D) covalent bonds between adjacent bases in one strand. 
E) ionic interactions with metal ions.

Question 9

How are a nucleoside and a nucleotide similar and how are they different?

Accepted Answer

Both have a nitrogenous base a

Question 10

In the Watson-Crick structure of DNA,the:

Accepted Answer

A) absence of 2'-hydroxyl groups allows bases to lie perpendicular to the helical axis. 
B) adenine content of one strand must equal the thymine content of the same strand. 
C) nucleotides are arranged in the A-form. 
D) purine content (fraction of bases that are purines)must be the same in both strands. 
E) two strands are parallel. 
A) absence of 2'-hydroxyl groups allows bases to lie perpendicular to the helical axis. 
B) adenine content of one strand must equal the thymine content of the same strand. 
C) nucleotides are arranged in the A-form. 
D) purine content (fraction of bases that are purines)must be the same in both strands. 
E) two strands are parallel.

Question 11

Double-stranded regions of RNA:

Accepted Answer

A) are less stable than double-stranded regions of DNA. 
B) can be observed in the laboratory,but probably have no biological relevance. 
C) can form between two self-complementary regions of the same single strand of RNA. 
D) do not occur. 
E) have the two strands arranged in parallel (unlike those of DNA,which are antiparallel). 
A) are less stable than double-stranded regions of DNA. 
B) can be observed in the laboratory,but probably have no biological relevance. 
C) can form between two self-complementary regions of the same single strand of RNA. 
D) do not occur. 
E) have the two strands arranged in parallel (unlike those of DNA,which are antiparallel).

Question 12

Which of the following is not true of all naturally occurring DNA?

Accepted Answer

A) Deoxyribose units are connected by 3',5'-phosphodiester bonds. 
B) The amount of A always equals the amount of T. 
C) The ratio A+T/G+C is constant for all natural DNAs. 
D) The two complementary strands are antiparallel. 
E) Two hydrogen bonds form between A and T. 
A) Deoxyribose units are connected by 3',5'-phosphodiester bonds. 
B) The amount of A always equals the amount of T. 
C) The ratio A+T/G+C is constant for all natural DNAs. 
D) The two complementary strands are antiparallel. 
E) Two hydrogen bonds form between A and T.

Question 13

A major component of RNA but not of DNA is:

Accepted Answer

A) adenine. 
B) cytosine. 
C) guanine. 
D) thymine. 
E) uracil. 
A) adenine. 
B) cytosine. 
C) guanine. 
D) thymine. 
E) uracil.

Question 14

The "energy carrier" ATP is an example of a(n):

Accepted Answer

A) deoxyribonucleoside triphosphate 
B) di-nucleotide 
C) peptide 
D) ribonucleotide 
E) ribonucleoside triphosphate 
A) deoxyribonucleoside triphosphate 
B) di-nucleotide 
C) peptide 
D) ribonucleotide 
E) ribonucleoside triphosphate

Question 15

In the Watson-Crick model for the DNA double helix,which of the following is not true?

Accepted Answer

A) The two strands run anti-parallel to one another. 
B) The base-pairing occurs on the inside of the double helix. 
C) The double helix is right-handed. 
D) There are two equally sized grooves that run up the sides of the helix. 
E) The two strands have complementary sequences. 
A) The two strands run anti-parallel to one another. 
B) The base-pairing occurs on the inside of the double helix. 
C) The double helix is right-handed. 
D) There are two equally sized grooves that run up the sides of the helix. 
E) The two strands have complementary sequences.

Question 16

Which of the following deoxyoligonucleotides will hybridize with a DNA containing the sequence (5')AGACTGGTC(3')?

Accepted Answer

A) (5')CTCATTGAG(3') 
B) (5')GACCAGTCT(3') 
C) (5')GAGTCAACT(3') 
D) (5')TCTGACCAG(3') 
E) (5')TCTGGATCT(3') 
A) (5')CTCATTGAG(3') 
B) (5')GACCAGTCT(3') 
C) (5')GAGTCAACT(3') 
D) (5')TCTGACCAG(3') 
E) (5')TCTGGATCT(3')

Question 17

The composition (mole fraction)of one of the strands of a double-helical DNA is [A] = 0.3,and [G] = 0.24.Calculate the following,if possible.If impossible,write "I."
For the same strand:
[T] = (a)____
[C] = (b)____
[T] + [C] = (c)____
For the other strand:
[A] = (d)____
[T] = (e)____
[A] + [T] = (f)____
[G] = (g)____
[C] = (h)____
[G] + [C] = (i)____

Accepted Answer

(a)I; 
(b)I; 
(c)0.4

Question 18

The phosphodiester bond that joins adjacent nucleotides in DNA:

Accepted Answer

A) associates ionically with metal ions,polyamines,and proteins. 
B) is positively charged. 
C) is susceptible to alkaline hydrolysis. 
D) Links C-2 of one base to C-3 of the next. 
E) links C-3 of deoxyribose to N-1 of thymine or cytosine. 
A) associates ionically with metal ions,polyamines,and proteins. 
B) is positively charged. 
C) is susceptible to alkaline hydrolysis. 
D) Links C-2 of one base to C-3 of the next. 
E) links C-3 of deoxyribose to N-1 of thymine or cytosine.

Question 19

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)?

Accepted Answer

Lower ionic strength reduces the screeni

Question 20

In the chemical synthesis of DNA:

Accepted Answer

A) the dimethoxytrityl (DMT)group catalyzes formation of the phosphodiester bond. 
B) the direction of synthesis is 5' to 3'. 
C) the maximum length of oligonucleotide that can be synthesized is 8-10 nucleotides. 
D) the nucleotide initially attached to the silica gel support will become the 3' end of the finished product. 
E) the protecting cyanoethyl groups are removed after each step. 
A) the dimethoxytrityl (DMT)group catalyzes formation of the phosphodiester bond. 
B) the direction of synthesis is 5' to 3'. 
C) the maximum length of oligonucleotide that can be synthesized is 8-10 nucleotides. 
D) the nucleotide initially attached to the silica gel support will become the 3' end of the finished product. 
E) the protecting cyanoethyl groups are removed after each step.

Exam 8: Nucleotides and Nucleic Acids

Describe qualitatively how the tm for a double-stranded DNA depends on its nucleotide composition.

Match the type of bond with the role below: -

For the oligoribonucleotide pACGUAC:

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):

When double-stranded DNA is heated at neutral pH,which change does not occur?

Which of the following are possible base compositions for single-stranded RNA?

Which one of the following is true of the pentoses found in nucleic acids?

For the helix in double-stranded B-form DNA,the majority of the stability can be attributed to:

How are a nucleoside and a nucleotide similar and how are they different?

In the Watson-Crick structure of DNA,the:

Double-stranded regions of RNA:

Which of the following is not true of all naturally occurring DNA?

A major component of RNA but not of DNA is:

The "energy carrier" ATP is an example of a(n):

In the Watson-Crick model for the DNA double helix,which of the following is not true?

Which of the following deoxyoligonucleotides will hybridize with a DNA containing the sequence (5')AGACTGGTC(3')?

The phosphodiester bond that joins adjacent nucleotides in DNA:

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)?

In the chemical synthesis of DNA:

The Foundations of Biochemistry

Water

Amino Acids, peptides, and Proteins

The Three-Dimensional Structure of Proteins

Protein Function

Enzymes

Carbohydrates and Glycobiology

Recombinant Dna Technology

Lipids

Biological Membranes and Transport

Biosignaling

Principles of Bioenergetics

Glycolysis, gluconeogenesis, and the Pentose Phosphate Pathway

Principles of Metabolic Regulation

The Citric Acid Cycle

Fatty Acid Catabolism

Amino Acid Oxidation and the Production of Urea

Oxidative Phosphorylation and Photophosphorylation

Carbohydrate Biosynthesis in Plants and Bacteria

Lipid Biosynthesis

Biosynthesis of Amino Acids, nucleotides, and Related Molecules

Integration and Hormonal Regulation of Mammalian Metabolism

Genes and Chromosomes

Dna Metabolism

Rna Metabolism

Protein Metabolism

Regulation of Gene Expression

Filters

Describe qualitatively how the t_m for a double-stranded DNA depends on its nucleotide composition.